Philipp Lenssen of Google Blogoscoped, Nikolai Kordulla and Dominik Schmid have just released a nifty new website called Sketchory. The site features over 250,000 sketches (cartoons, scribbles and other fascinating artwork) that you can copy, remix, embed, view as animation and so on.
The sketches use Creative Commons license, so you're free to use it even in commercial settings (say, create a book of sketches - with a maximum of 1,000 images).
Check it out: http://sketchory.com/ - Thanks Philipp!