Recently I noticed that there was a new release for Trackmania Nations (the free version of Trackmania that people all over the world play). This new version is supposedly new and improved, and integrates Trackmania United (the retail release) and Trackmania Nations (the free release) into one.
First of all, you might ask what is this game? Trackmania is a game that involves you driving cars on surreal tracks (kinda like slot car racing except you can steer). Your car travels quite fast, and the tracks are very varied and can get quite wild with large jumps, half-pipes and loops at times. There are a few different game modes too, like time attack (my favourite online) and stuntmode and so on.
One of the key draws to this game other than just the racing is the customisation of everything. First of all, as one might expect, you can make extensively crafted tracks of your own using the comprehensive editor and release it online for all to try out and enjoy. Not only that but if you have the skills you can give your cars custom paint-jobs in-game as well as import custom models made by other people (or yourself if you're lucky enough to have the skill).
Combine this with a robust and competitve online mode and you've got one fun (free) game. It even has a decent single-player component with the medals earnt there for beating certain times going onto your profile and increasing your global rank. Your rank is also affected by playing online with other players and beating their times.
All in all its a really fun free game, its worth the 500MB download (it looks nice too - and runs good as well).