This might already be well-known but I've never spotted it before. If you right-click a Stickies note, there's an option for Capture Selection from Screen. This effectively brings-up the screengrab tool and you can click and drag to not only capture part of the screen, but also automatically insert it into the note. If you use Stickies for research and note-making purposes, like I do, this is a superb and fuss-free way to grab a photograph or diagram from a web page, or even a document you're reading (or a block of text if you can't be bothered to cut and paste).
[crarko adds: I tested this, and it works as described. Stickies has been around forever (since System 7.5), and there are many hints about it. This seems to be a new thing added to the program in Snow Leopard; I looked at a 10.5 version and the contextual menus did not have this option.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20100823075951280