this might not be new to OS X, and/or this might be common knowledge - but it suprised the heck out of me... holding down the OPTION key while scrolling through a text window speeds up the scroll considerably (tested in BBEdit + TextEdit). great for code or getting through logs...
[Editor: I'm not sure when this was added, but it was news to me, too! Thanks for the tip, Anonymous!]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20010911095522350