I DO NOT RECOMMEND the Linksys WRT54G. It has had a lot of issues with Macs recently. I think there are fixes and a lot of post on this site about them.
I bought one, it worked for a day then stopped, called Linksys they said it was working fine, called Apple they said it was Linksys' problem. Called Linksys again, couldn't talk to anyone that new how to troubleshoot on a Mac (or what it was for that matter). I will never buy a Linksys again. I bought a D-Link WBR1310. It works great, the range is almost perfect at 40 feet and through three interior walls.
Summary: The Linksys WRT54G is known to have issues with Macs, may or may not be fixed, may or may not work. There a lot of comparably priced alternatives that works as well if not better. Go for the D-Link.