I’ve been tinkering with dd-wrt firmware, what an incredible piece of open source software. 

Repeater Bridge (Same as primary network to bridge)
http://www.dd-wrt.com/wiki/index.php/Image:Repeater_Bridge.jp

Repeater (Different network from primary)
http://airfart.blogspot.com/2008/03/how-to-set-up-wifi-repeater-mode-on-dd.html

Stay tuned!  More references to come