For posterity, a pretty exhaustive list of decent stock agencies.

Royalty-free

AbleStock (Over 16,000 royalty-free digital images – New!
Artbeats (see the 500 still images – mostly footage though)
Artbitz – vector art: bold, beautiful & affordable
Artdisc royalty-free illustrations
Corbis
Central Stock
Clipart.com subscription-based access
Comstock
Creatas
*Digital Vision great if you need that bright, spotless office look
Fotosearch Stock Photography A “portal” which allows users to search from more than fifty quality stock photography vendors at one site. They can also find clipart pictures, royalty-free illustrations, royalty-free motion stock video clips, royalty free vector maps, and background clip art imagery.
Four Palms
*Getty Images includes Artville, Digital Vision, Eyewire and Photodisc
Photos To Go
Painet
West Stock
Photo Site of the Week links to individual photographer’s sites
Lots of Stock Links if our hand-picked selection isn’t enough
Rubberball specializing in all your bubble-headed people needs

 

Rights-managed

Masterfile
*TonyStone cutting-edge conceptual stuff
Image Finder which seems to be from several libraries
Indexed Visuals submitted by a brain fuel reader

 

Free stock agencies

STOCK.XCHNG
istockphoto.com Collection of 32,000+ royalty free files, this is a community of artists
MorgueFile very nice flash interface
TastyStock

* indicates a BrainFuel favorite.