What I want to do..

I want to buy a 19" LCD screen, turn it on the side and use Xinerama. Then I can have one monitor for documents and one for everything else (and because it is a lovely Iiyama CRT, it's perfect for games).

So I need to know, is it easy to configure Xinerama to have different resolutions for the two DISPLAYs? Can I run games so that they only use DISPLAY:1? When I do this with games is it a good idea to blank (disable output) to the other screen? I hope not since it would be too much fun to play Quake III and still use my IM at the same time!

Any people know if this is possible out there?

I got a detailed response from Arteaga-Mejia Luis, many thanks to him!

I went into your site today and did read the "Help me!" section. I am a GNU/Linux user and also have Xinerama at home with two 19" monitors and 1154x1028 resolution in each one.
As far as I've seen, configuring the two screens with different resolutions it's very possible. The only thing you cannot do is have two different bit depths. You must use the same bit depth (i.e. 24 bit is the one I use) for both your screens.
Yes, your game may use only ONE display. I don't game at my PC, but I certainly watch movies. I can set a movie to "full screen" in one of the displays and continue working in the other.
I just love Xinerama and find difficult to work anymore without it. A few days ago one of my graphic cards went dead and I spent the whole week without working at my machine, because without the two monitors it's not longer fun. I've got a new graphics card at the weekend and I am happy again.
Hope this helps you!

If you have any questions, please contact me. I really look forward to hearing from you!