It's been a while since I found some new games to play, but rummaging around, I've come across Java Gameplay. They've got a series of nice games in the "Nice to kill a half hour" variety. What's nice is they've kept older versions of the games online so you can see the sort of evolution of the games. Older wireframe games give way to texture mapped realistic landscapes, etc. Warzone is a first-person tank game that has gone through this progression.
This game is sort of "Battlezone 2000" - take the old Atari wireframe Battlezone game and take it into the modern age. You have multiple tanks to choose from, missions, complex landscapes, and a turret that can actually turn in a different direction than the tank is facing. The gameplay is good, sound and graphics are quite nice for a Java embedded app, and it runs along nicely on my IBM T40 laptop.
Java Gameplay has several other cute little shoot 'em up games available. I've found myself going back there a few times to just blow things up for a while to unwind from a busy coding day.
