Following up on Falk Bergman's discovery that the mozilla-based Help browser can be redirected <http://forums.secondlife.com/showthread.php?t=110747>, here's an explicit set of instructions for Mac users:
1. X.4 users: open Spotlight, type "Secondlife" & click on the folder that comes up. X.3 users: open a window in the Finder & click on your username in the left-hand pane (right under Desktop), then go to Library > Application Support > Secondlife.
2. Open the folder called "user_settings"
3. Double-click on the file called "settings.ini"; if there's no default application associated with the file, choose TextEdit.
4. Scroll down until you see the entry for HtmlHelpRec; just above that entry, insert the following line:
HtmlHelpLastPage http://del.icio.us/home
--del.icio.us seemed like the most sensible choice to me, but you should substitute the URL for whatever page you want. (I put the line where I did just to keep things orderly, ie "best practice," but it doesn't _have_ to go there.)
5. Save & close
The next time you open up SL, go to Help & select the Second Life Help (or hit F1). When the browser window opens, you should be looking at your new homepage! Good luck & happy browsing.