I use 2 17" LCD monitors, one Sony and one Samsung. I find it very convenient for video editing and web browsing. Hopefully next year I will also get some CAD usage out of it (better start learning).
I really don't understand how people can dual monitor with 2 different monitor sizes. I would go crazy using a 17" and a 19" right next to each other.
Here is my setup:
(I know my desktop looks empty, but wait until you press start. That's the real reason I have 2 monitors

)