For you Mac OS X users out there, a tiny application called Paparazzi! that takes a URL and renders it as a ful-length bitmap, which you can save and edit. If you try it on an LJ journal or friends page, you get a very tall image !
It doesn't even allow you to paste URLs into the text field at the top, but it's still very cool. [Via Giles Turnbull at O'Reilly MacDevCenter.]