I don't have anything too big since I game in an office-type set-up.
360 and PS3 on this 23" 1080P ASUS LCD LED-lit monitor.

Wii, PSP, and sometimes the PS3/360 (usually just used when I play Kinect) on a 19" Toshiba LCD HDTV.

PS2, Game Cube, and Dreamcast on this old Samsung SDTV. It can do 480P but the quality isn't as good as I remember it. There was some method to unlock 1080i from the service menu, but my brother had this TV for a few years and he lost the remote.

There's also this 25.5" ASUS 1080P monitor in the same room, currently (barely) used by my wife.

Still have an old Samsung GXTV sitting in the bedroom, too. No idea what to do with it.
Gonna buy a 40"+ HDTV soon I think, but deciding between LCD, LED, Plasma, and DLP is gonna be tough.