Buying Royalty Free Stock art

I like CLKER.com (Caps are just for ease of reading). They've some neat stuff to at least get prototyped stuff onto the table (and some others that are good for camera-ready art). Features both photos and line-art, but the photos tend to bend more towards military stuff, planes on aircraft carriers and whatnot. Their search is a little "meh" so when you enter a string, make it pretty general. Very strong on people-doing-stuff and computer/Powerpoint-friendly kinds of art, but some straight up bizarre stuff too (my personal favorite is the b/w image of a dude in a tie/suit, complete with riot helmet and pump action shot gun...what?). They also do a thing where they will, for free, vectorize/rasterize your uploaded photo or pic. I've seen some very-obviously-taken from MS Office stuff that they've kung-fu'ed just enough to more than likely make it fair-use. And, in a weird twist, they have LOADS of stuff from the US Library of Congress-- engravings and illustration "plates" from old books, public health posters, etc. Weird stuff. The webmaster's a decent dude too; very "take if you need, leave if you can" kinda rules on contributing.

Photos can be had at morgueFile.com and iStockphoto, but I think iStock is maybe pay for some of their stuff. Also, MorgueFile's webmaster's kind of a jerk when you email him for legality questions. Like, sersiously? Don't be that guy. Both are kinda limited-- obviously since it's photos, it's real-world kinda stuff.