Those who have been here for years and are now wondering why people are making such a fuss about Minecraft, this could interest you.
Starting with version 1.3, released yesterday, the game includes a free demo mode. Create an account, download the launcher, and start it using your new account. You'll be offered a "Play Demo" option, which allows you 100 minutes of gameplay. You won't be able to join any servers, but it can give you a better idea of what the game has to offer... or if your computer can run it!
Topic: Free demo available!