When I purchased my Linksys BEFSX41 I had two spare wireless routers a D-Link WBR-1310 and a WBR-2310 respectively. What to do? Turn them into wireless AP's (access points) of course! Increase your wireless coverage, look cool!
First thing's first, set up DHCP on your main router. For me it's the BEFSX41. Set your DHCP range, for example 192.168.0.150-199 giving you some room for wireless devices.
Now login to your router (most likely 192.168.x.1) which is converting to an AP, the WBR-1310/2310 for me. Turn DHCP off and set the router IP to below or above the DHCP range. So for example, 192.168.0.149, 192.168.0.200 etc.
Once you have configured your AP, plug the ethernet cable into one of the LAN ports, not the WAN port. See below.
Check the LAN connection then check the AP wireless connection.
This method can work with more access points as well (in my case, two AP's).
What now? Well, if you have two [802.11b/g] AP's set them to non-overlapping channels. Change them to either channels 1, 6 or 11. For more info see here.
Comments, ideas and so forth are appreciated :)