I like using a 30" plus a rotated 22" screen.
http://blog.domaintools.com/2007/12/quad-monitors-117-millio...
http://blog.domaintools.com/2007/12/quad-monitors-117-millio...
I also use a rig of 3/4 in. natural gas pipes and some cheap VESA wall mounts that let me position my monitors however I like.