Maybe this obscure key combination will be unnecessary when Panther comes out, but so far I have been unable to find a menu item for inserting page breaks in TextEdit. I forget where I read this, but it turns out that you can insert a page-break code by using the keyboard and typing Control-Q followed by control-L.
The result won't be obvious unless the document is in Wrap to Page mode (Command-Shift-W).
Mac OS X Hints
http://hints.macworld.com/article.php?story=20031020191248233