WiFi repeaters cost more than a router.

If you have sufficient wired network, but want to extend the range of an existing wireless router over a large area, the simplest, cheapest way to do it is with your garden variety Linksys WRT54G routers -- you don't even need to flash them to the Linux firmware.

I derived these instructions after searching all over the Internets, and I don't remember the source, so I've got to re-post them for my own reference -- and that of anyone else who wants to do this.

• Connect a computer to the new, second router. Enter the router admin page using your browser.
• Disable the DHCP server
• Change the local IP address to be in the same subnet as the primary router, but below the range assigned by it's DHCP server.
  • For example, your primary router probably has a local address of 192.168.1.1 and assigns IPs in the range 192.168.1.100 to 192.168.1.150. In this case, a safe IP for you to use in your second router would be 192.168.1.2 -- this also makes it easy to find later!
• Apply the changes. (some reboots may be necessary)
• Plug your wired network into one of the standard LAN ports on the new router -- do not use the Internet/WAN port.
• Reconnect to the admin page using the new IP address you just gave it.
• Find the Advanced Routing page and change the router's operating mode from Gateway to Router.
• Configure the wireless settings of the new router to exactly match the wireless settings of your primary router (including SSID and security) but use a different wireless channel. Most sites recommend spacing out your channels by 3 or 4 to avoid interference and bleed.
  • For example, if your primary router is providing wireless on Channel 6, your secondary router could safely use Channel 2 or Channel 10.

Once these steps are done, laptops will be able to roam freely between access points, and will switch, without interruption, to the strongest available signal. I've used this successfully with 2-3 routers, and have had a strong, stable wireless network since.