T R E M U L O U S :: NEWS - One of the most original FPS + RTS games I've seen. DretchStorm tends to be one of my favourite servers. I play as Noob Nibbler.
EVE Online - I played as Trichobezoar for about 2 months. Interesting business & economy sim. Oh, there's some space graphics too, but it's pretty much just empty eye-candy.
Vendetta Online - Space Combat MMORPG for Windows, Mac and Linux - Also played this for about 2 months, a bit more during the early beta days. I don't like it as much since it became more EVE-like with licenses and all, but overall I like the gameplay better. The physics still aren't much better than Wing Commander, though.