1. 20 x 200
2. Society 6
3. Whisper Editions
4. Sonic Editions
5. The Library of Congress
Another option, although it is not a quick fix, is to go to a Grad school's Open Studio Tours. If there is an art school, or an art program near you, visit their studio's and you may find the next big artist, or at least a great piece of work.
Now get to prepping the wine and cheese for your next Art Opening.