19 on my pc and my imac is a 20. I dunno what I'd do with dual monitors. . . I mean I do video editing and stuff but I'm content with the amount of resolution I've got. Maybe if I was editing something over 30 minutes it might come in handy though. . .
I run two for audio production reasons mostly. I keep Reason going on on one and FL Studio on the other. Other wise in Vegas I use the second for a live preview.
At both home and work I use dual 19" monitors for the pcs I use to do most of my research and writing.
(at home I also have the laptop and the gaming pc with a 36" Gateway Destination - come to think of it, I have a dual monitor setup with the home gaming pc too - I've got a 15" lcd plugged in to, especially because the gateway only does 800x600)
Consoles: Wii, Xbox 360, Nintendo DS, Xbox (x3), Gamecube (x3), Playstation 2 (x2), Dreamcast (x2), Nintendo 64 (x2), Playstation 1 (x3), Saturn, SNES (x2), Sega 32X, Sega CD, Genesis (x4), Gameboy Color, NES.
Dual 15s at home, but the 22 next to it is also hooked up if I want to watch a video or some such. Eventually I will update to more lcds, or those two other 22s in the closet. But first I will need a proper desk, not the mightlylite tables I am using right now.
Back in college, in 1999, I ran dual monitors with a 17" and a 15", but that was on a Mac. At that time it was a PITA to run dual monitors on Windows 98 because it didn't do such things natively well at all. Nowdays I only have one monitor worth viewing, so only one monitor at a time, though even Windows XP has some weirdness with multiple monitors that the old Mac never had...