The free version of Trackmania 1 that we all loved has been updated for Trackmania 2! You can currently preorder it on steam (btw TM2 is on Steam finally) for $10. Although I have also read that, after launch, there will be a free version of Stadium with time-trial only multiplayer and a demo campaign just like in TM1. Hopefully this will revitalize the community since TM2 has kind of died. I was talking to a server admin earlier and apparently you can convert old TM1 maps into TM2 maps, so... instant map library. It all sounds pretty awesome.
You can get in the beta by simply downloading the TM2 Stadium demo through Steam.