Playcrafter.com is a free site which lets you build and customize your own games based on five different templates including a brick, golf and marble game.
Sound boring? It is actually deceptively addictive because you can add all kinds of obstacles, customize colors, backgrounds, add music and even upload your own images. Once you are finished you can play the game, share it with friends and add it to the gallery to show off your work.
It is extremely easy to use with a drag and drop interface. Before you dismiss it, take a look at the gallery of games already created to get an idea of just how much you can do with it.
Even better, if you sign up now you get entry into a competition to win either a Wii, Playstation 3 or XBox 360.