dunno if somebody else has pointed this one out already:
in the general controls panel one can specify how clicks in the scrollbar are handled: old-style mac os-way (scroll one page) or next-style (scroll to that position).
whatever you choose: holding the option-key (alt) while clicking toggles the behavior. :)
comes in handy on long web-pages...
Mac OS X Hints
http://hints.macworld.com/article.php?story=20010416120139620