I am very fond of the site Tiny Showcase. Since 2004, they've been offering limited edition prints of tiny-sized (and thus, affordable) artwork, with a percentage of the money from each print that's sold going to a charity of the artist's choice.
This week's print is One Way Out by Sasha Barr. It's in an edition of 100, measures 4.25"x6" (plus boarder for framing), and you can get it here for only $20.
The prints are posted every Tuesday evening and are available for sale until the entire limited-edition run is sold out. As there is much amazing work from many wonderful artists that gets featured, some of the prints sell out fairly quickly, but you can still find some interesting stuff in their store, or you can simply browse through the past editions in the gallery. Keep up the good work guys!