Is anyone out there playing Spelunky? Shea and I have become somewhat addicted by it, and I am surprised there isn't a forum topic about it yet. It is really must-have for anyone from the 8-bit console generation, and best of all, it is being freely released by its developer Derek Yu.
The game is essentially a platformer with procedurally generated levels where you play as an Indiana Jones type character searching for treasure and saving damsels in distress. The game is very unforgiving in that you will die a lot. Man-eating plants, the undead, spikes, arrow traps, bottomless pits, angry shopkeepers with shotguns are just some of the ways you will die. But, like Dwarf Fortress, losing is fun, and you'll always be eager to start up another game. There are also a lot of secrets to discover and items to try out.
You won't likely ever spend more than 10 minutes in a game, so there isn't a huge time commitment involved. Give it a try and tell me what you think!