This morning I saw ReadWriteWeb's 3 cool sites to bookmark your favorite images on the Web, and now I'm trying one of the sites: vi.sualize.us (my account).
As the article says, "You can think of it as the Delicious for images", and vi.sualize.us really is very Delicious-like, complete with a Firefox extension, tags, and a history page for each item.
When you see an image you'd like to bookmark (and provided you have the Firefox extension - I don't know how it works with other browsers), you just right-click it and then fill in the details on a little pop-up window. Each saved image links back to the original, and vi.sualize.us does encourage people to look for the author's name - which is more than can be said for any other site I've seen. (Take a look at some Delicious links, for example; hardly any of them name the author.)
There are probably hideous and horrible copyright implications, but bah phooey. Cite your sources. Share your work. Cross your fingers.