Windows: When it comes to voice chats on the web, Skype is definitely the way to go. This awesome app - chosen by three Softonic editors as top of the decade - keeps on improving with every new version. The latest one, Skype 4.2 Beta, features call quality indicator, Google Chrome extension, enhanced support for the Windows 7 taskbar and the ability to transfer calls.

iPhone: If you're growing tired of the default Clock feature on your iPhone and want a new way of waking up then check out Alarm Clock Free. This handy app turns your iPod into a stylish digital clock and alarm. The neon green-on-black clock skin bears a striking resemblance to Night Stand, but this is no bad thing, as it looks good and is easy to see from a distance.

Mac: There are few Mac applications that can compete with VLC Player when it comes to playing video but MPlayerOSX is a very decent attempt to do so. MPlayerOSX impresses by playing virtually any video file type. These include MPEG/VOB, AVI, Ogg/OGM, WMA/WMV, QT/MOV/MP4, RealMedia, Matroska, and many many more. It may be a little rough around the edges in places compared to VLC Player but it's definitely worth a try.

Windows: More and more people work with dual monitor PCs today, and while this can help productivity, it's not always easy to find nice wallpapers wide enough to stretch between them. This pack of 20 Dual-Monitor Wallpapers gives you a wide selection of high quality images to choose from, designed specifically to suit dual monitors.

Mac: If you haven't installed Flip4Mac WMV on your Mac yet then how on Earth have you survived without it? Flip4Mac WMV is an essential collection of QuickTime components that allow you to play, import, and export Windows Media video and audio files on your Mac using your favorite QuickTime-based applications.

iPhone: If you're trying to stir up some Christmas spirit then I recommend you take a look - or rather a listen - at Christmas Sounds. This is a collection of 16 different festive noises and music, all available to play by clicking on an icon. Each icon is decorated with a fun seasonal image that represents the audio hidden behind it.

Just two more days until Christmas and that's two more days in which to check out great software before you get  interrupted by the festivities. Have a look behind the window to find one of Niamh's top apps of the year.

xxx is a great application that allows you to create stick figure animations that range from the simple to impressive - with a little time and patience. Working on the normal basics of stick figure animation, create individual frames of action and then view them in sequence, producing the animation. Move over Disney, xxx has come to town! - Niamh

Windows: The default Task Manager shipped with Windows is often not enough. In these cases, you should use System Manager, a complete task management tool that includes information about everything that's brewing in your system: active processes and services, installed drivers, start-up apps, network connections and more.

Mac: The latest version of Firefox 3.6 (Beta 6) is now available gives you a taste of what's to come from the best web browser out there. There aren't really any revolutionary changes in Firefox 3.6 Beta as the look remains the same but some handy new features have been introduced such as integration with Personas and a new intelligent add-ons manager which updates automatically.

iPhone:Since Amazon introduced its Kindle device, the whole World has gone eBook crazy. Trains are now full of commuters gazing at digital displays rather than thumbing through paperbacks. If you haven't got a Kindle and want to know what all the fuss is about - or if you have a Kindle and want to enjoy the books you've already purchased for it on your iPhone - then install the free Kindle for iPhone app.

As we roll towards the end of our advent calendar, here's a fun game that Jon seemed to be glued to the whole year. Take a peek behind the window to reveal what it is...

You control a guy on a pogo, and have to jump on the pigs and bats to score, against the clock. High scores can be racked up by executing combos. The mechanics of xxx are simple, and work well. While it's a really simple concept, it's surprisingly addictive, and the online scoreboard gives you the urge to push for even greater high scores - Jon

Welcome to a new day in the OnSoftware advent calendar. Today's window hides behind it one of Jon's favorite games of the last year. Surprise, surprise it's a bizarre indie game so you'll probably have never heard of it, but take a blind guess if you like.

xxx is a macabre and dark beat 'em up. Created over seven years by one developer, it has almost all the options you'll find in a commercial beat 'em up, presented in a completely unique style. The characters are very unusual, and may put some players off. But if you can accept the strange cartoon fighters, there's a lot of depth here - Jon

Window number 19 of our advent calendar hides behind it another big game release of 2009. See if you can guess what it is before plunging through the window below.

As per usual, xxx includes a database of leagues, teams and players that the CIA would be proud of. The game is fully licensed and allows you to play in the major leagues from around the World, with access to a dizzying array of facts and figures on all the players - James

It's now only one week until the big day and I'm sure excitement is starting to set in. Perhaps you're trying to sort out your Christmas entertainment. If so, take a peek inside today's window and you might find something that will help you.

xxx lets you transform your standard home computer into a multimedia hub from which you can manage your local media files as well as a wealth of online media sources such as Flickr, Pandora, YouTube, Icanhascheezburger and LastFM, among many others - Niamh

Another piece of Mac software for day 17 of the advent calendar. It's a popular Windows app that finally got its Mac release at the start of the year. See if you can guess what it is before you dive through the window.

Slick, polished, quick, logical and easy to use, xxx makes viewing and publishing photos and videos a dream - I'll never go back to iPhoto again - Nick

Window number 16 of the advent calendar hides a major game release of 2009. Elena likes this game so much she included it in her top ten apps of the decade.

xxx is the long-awaited new version of the popular EA franchise. Like in previous titles, the game has no fixed end: your aim consists of creating a human-like creature and managing their existence, looking after all aspects of their lives, from controlling their bladder to achieving the highest position in their professional career. It is truly an excellent successor, including many great features that make the game even more enjoyable.

Windows: If, like the Softonic editors, you're also hooked to Twitter, you'll love Saezuri. This AIR-based desktop client will make your Twitter experience much better! Includes all the tools you would expect (view and send tweets, support for multiple accounts, built-in URL shortener, photo uploader...) all wrapped up in a nicely designed interface.

iPhone: Google Earth for iPhone, successfully brings the best free mapping tool on the planet to the Apple device. The application uses the same satellite and aerial photography found in the desktop version, only this time you navigate the globe simply by swishing your fingers across the screen. This latest update of the app is now 10Mb so WiFi is no longer required to download it.

Mac: Macs have always excelled at Desktop Publishing although applications like Quark are neither simple nor cheap. However Swift Publisher makes it easy enough for anyone to produce professional looking flyers, newsletters, brochures, letterheads and more. There are more than 1,000 images, 90 designs and 100 templates to help get you going too, so you don't have to start from scratch.

Today's advent calendar features an Android app I tested earlier this year and couldn't get enough of. If you're a fan of the Google mobile OS, this is my Christmas gift to you...

If you can't be bothered going through the hassle of being on a reality show, just install xxx on your phone and beam yourself live across the Internet for the World to watch. The xxx project is an ambitious and exciting one and once the technology really gets off the ground, the scope of its uses for entertainment, communication, and education will be huge - James

Today's advent calendar window hides behind it one of Jon's favorite games of 2009. It's not the most well-known of the titles we've been playing this year but it's great fun nonetheless.

xxx is a puzzle game that will remind some of the highly-rated Portal. Instead of that games portal creating gun, you have a gravity gun that can attract or repel objects. It is an interesting puzzle game, and is absolutely fantastic quality for a free game - Jon

The number thirteen might be unlucky for some, but not for this application, which makes it into our list of 2009's top software. It's unlikely you'll guess this one because the program is relatively unheard of - but have a stab at it anyway!

All writers suffer from writers block from time to time, and xxx is a tool designed specifically to overcome it. xxx consists of a very basic word processing program with absolutely no frills. You set a word target and a time limit and start writing. If you don't meet the target within the time limit, xxx erases all your work. If that isn't motivation, I don't know what is! - Niamh

Windows: My favorite app to manage photos is undoubtedly Picasa. Google's great photo app has just hit version 3.6 with great new features, such as an improved tagging experience, the ability to geotag your images, an enhaced importing system and above all, the all new collaborative web photo albums.

iPhone: If you need to get something noted down quickly it can often be better to dictate it. Not all of us have a personal secretary following us around though, and for these people Dragon Dictation could be the answer. This free app records your voice and converts it into text in a very simple fashion. After loading Dragon Dictation just click on the record button and start talking.

Mac: Formerly known as simply Episode and Compression Master, Episode Encoder is a superb tool for compressing and encoding video. In terms of speed, it's one of the quickest encoders you'll ever use and even better, it has a user friendly interface that makes managing and encoding video a pleasure. Episode Encoder is ideal for those who need to compress and distribute video via the Web, DVD, mobile phones and portable devices.