Haha, forgot to give the post a title so Blogger gave it this interesting one instead!
Damnation of the Gods is a project to make a game similar to Dungeon Master and the Eye of the Beholder series. For those not familiar with them, they are pseudo 3D RPGs - that is you have a first person view but you can only move on a grid (i.e. north, south, east, west) and the graphics are generally 2D sprites for both the environment and game characters. Unlike roguelikes the game is realtime so waiting around is not advisable. There's only a couple of screenshots but they show a fair amount of progress. You can play the latest version (0.17) on Linux or (via MingW) Windows. The author slightly confuses the term freeware with open source on the homepage but DotG is definitely open source.
Eye of the Beholder II was one of my favourite games when I was growing up. It was challenging, immersive, and had excellent graphics for it's time. It was a tough game, and I don't think me or my brother ever completed it despite buying guides with full maps and solutions to each level.
There's an update to Thunder & Lightening, the 3D air combat game. This release provides only a Linux binary although if you are desparate to play on Windows, the author may cave into a few requests. With major gameplay enhancements, a tutorial mission, a new scripting language, and bugfixes, it looks worth checking out.
Another game I want to check out is Lengendary Legions. Although it looks similar to Wesnoth (fantasy hex-based strategy) I'm sure it has a character all of it's own but without playing it and with little explicit information on the website, I really need to download it and have a crack. There is a gameplay video but there's only so much you can discern from that especially with the, er, interesting music.
At the moment there is no AI so it's player vs player only (local or networked).Finally, you can get an unoffficial Linux binary of StarShip Troopers: Last Defense from here. YMMV.