The older demo system was changed to the current Channels system. Essentially, you can play the current Trackmania (or Shootmania) channel for free, regardless of what the title being used would normally require. The channel will cycle through different programs, usually letting you try out the different environments on community made maps. The channels should be the first thing you see once you log in to Maniaplanet. Being able to try out the titlepacks offline is no longer an option, unfortunately.