With LCDs things don't work that well. Dan's Data has ideas. The one I favor is bolded.
Dan's Data letters #178Dan likes the TVs because they're ppi are low compared to a computer display. I like the LCD option, but it's expensive. You have to pay a LOT to end up with something that's a bit better than an 800x600 display. Maybe an old CRT is really the best option.
1: Get a good-sized CRT monitor, like a 19 or 21 incher, and run it at a suitably low resolution. 1024 by 768 on a '21 inch' screen with a 20 inch real viewable diagonal gives about 64 pixels per inch.
2: Get a big LCD monitor and run it at less than its rated resolution. That'll give you a fuzzy picture as the monitor spreads displayed pixels around its physical pixels, but you should get sharp results if you can run at exactly half (or even a quarter) of the rated resolution.
The advantage of this strategy is that if someone with 20:20 vision wants to use the computer, they can crank the resolution back up. And some large LCD monitors actually cost about the same as similar-sized LCD TVs with much lower resolution. Dell's popular (jf: 24") 2407WFP is the best example; it currently lists for $US720 or something, has a rated resolution of 1920 by 1200, and should be easy to run and good-looking at 960 by 600. That'd give about 47 pixels per inch.
3: Use an LCD TV that does fit on the desk. There are plenty of mid-sized options, and a lot of them have 'RGB' inputs suitable for computers - many have a plain old 'VGA socket' on the back, and that usually means they can sync to normal computer output scan rates (you can't bet on a TV with a DVI socket on the back being able to take input at various resolutions or refresh rates)...
PS. I checked my iMac. It has a 21" display and the resolutions are 1680x1050 (what I use) and half that is 840x524. I didn't think 840x524 was any better than 1024x768.