Janni Kovacs has produced what I think is the first homebrew game for the Pre: Snakes.  Snakes is your typical ‘eat-and-grow-longer’ style game and I’m sure it will evolve nicely.  We’ll look forward to finding this on the App Catalog when Palm opens it up.  Unfortunately, if you’ve (been) updated to the 1.0.4 firmware you will need to follow the SDK app installation instructions (which is not for the faint of heart but is your only option for 1.0.4).  For more on installing homebrew apps you can check out this PreCentral post.