If you have a web browser that supports text clippings (as far as I know, OmniWeb is the only one), you can drag text from a web page to a text document (for example, an e-mail). This is really useful when a hint on macosxhints contains a shell script that you want to try out. Simply highlight the script and drag it onto a blank TextEdit document. No need to bother with typing out all that code or worry about making typos. Also, if there is information from a web site that you want to save, just highlight it and drag in to your desktop. I've got a folder of handy macosxhints text clippings myself.
[Editor's note: Clippings also work in Mozilla, IE, and iCab, and most (all?) other OS X apps. I seem to recall having problems with clippings in earlier versions of OS X (Cocoa apps worked, most Carbon apps didn't?), so I hadn't used them much recently. However, a brief test this morning showed that both Cocoa and Carbon apps seem to now support clippings perfectly well; the only exception is Java-based apps such as jEdit.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20020606090425408