Busy Plugboards
Once in awhile when I don't feel like doing anything that requires thought, I'll visit my list of sites that have plugboards and plug (add a tiny graphic to their advertising page). Over the months, I've come to know which plugboards are the busiest—not the busiest of all because I don't know of ALL the plugboards, but busiest of the ones on my list.
If you're looking for busy plugboards, here are a few:
http://host-plug.sakuradrops.org/
http://www.blogging101.com/plug-your-blog.php
http://www.middone.co.uk/plugboard.html
http://www.plugaholic.com/
http://www.plug-board.com/