I use a 19 inch HDTV as a computer monitor, and PS3 display. The computer is plugged into the VGA, and the PS3 is in the HDMI port. I got it for under $200 last year at circuit city. It's pretty good, nowhere near as good as the 32 inch toshiba HDTV I have though
Well, you are going to need an HDTV and the right cables. Assuming that you have a PS3 or a late release 360, you need an HDMI cable. These go for about 6-10$ shipped on ebay, and about 25-50$ in a store. Since its digital, the monster cables deliver the EXACT same picture as the off-brand from Hong Kong. Alternately you can do component which is slightly lower quality but you can get a combination PS3/360/Wii cable for about $20 at gamestop.
As for TVs, definatly go off brand. I have had an Astar, Olevia and Visio and the picture/sound quality easily rivals the big brands that cost 50% more. The key here is patience. There are deals to be had, but you have to catch them, and you have to take a risk and be willing to buy things with no return policy online. I got my 37'' Astar for 599$ a year ago and my dad got a 47'' 1080p for 1000$ last November. Don't settle for anything less than 32'' even if it means having to save up money for a few months, and if you go >42'' be sure to get 1080p, even though very few games support it.
If you want to watch Blue Ray Discs you should seek for Monitors that are supporting HDCP. Monitors with the HDReady sign do support HDCP but they have eventually no Full HD Resolution (1920x1080p). Remeber 1080i is evil because most of the devices dont own a good deinterlacer.