Personally, I usually don't like having the ruler visible in TextEdit -- it just bugs me. So if I want to add a list to my document, I have to make the ruler visible, and then select a list type from the list menu. Or I have to use the menu item if I want to create a customized list format. But what if I just want a plain old list, quick and easy?
Well, I just discovered that if you press Option-Tab at any point, the line which the cursor is currently on will turn into a dashed list item! Press Option-Tab again to indent the list item even further. Beyond that, it functions just like regular lists (hit return for another list item, double-return to decrease the indent, etc.).
The only problem I've had is that I don't know how to choose something other than dashed lists using the keyboard. Perhaps there's a hidden TextEdit preference setting for this...
[robg adds: This only works in 10.4, as TextEdit in 10.3 didn't support lists. And, of course, you must be in RTF mode, not Plain Text mode, to use this trick.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20051122224405807