For my PC and Xbox 360 (and a PS TRIPLE when I get one, since it has an HDMI port that's not being used at the moment) I use a 25.5" Samsung SyncMaster 2693HM. It's so bright and crisp it's almost scary, plus it can output 1080p, making it perfect for HD stuff. The sound goes through my PC and out my funtacular Logitech Z-2200 speaker set.
For everything else (Wii and under) I use my little 13" Samsung CRT TV. I don't really need anything bigger for 480i stuff, after all. Most of the stuff gets hooked up via composite through a couple of cheap GameStop 4-port A/V switches, with only two of my systems (a Master System and a Genesis) getting the RF treatment.