Linksys WRT54G ALL the way.
http://www.linksysinfo.org/index.php
http://www.wrt54g.net/forum/index.php
http://forum.bsr-clan.de/index.php?c=5
I have two of these beasties, both with third party firmware installed (to give many more features). Buy them new for £55+ or get them cheap on eBay or through Amazon (Used and New) - I got my second for £32 NEW!
I use one as a gateway and one as a range extender/AP - the firmware allows use of WDS meaning the routers are connected to each other wirelessly, not cabled as a normal repeater/AP needs. The ranges are excellent.