I prefer
dd-wrt compatible routers (dd-wrt is third party firmware). By coincidence, your WRT54GL already supports it, so you *could* convert it into a wireless Ethernet bridge and maybe buy another router. Not saying that’s the best decision, but just putting that out there for consideration.
DD-WRT Solutions:
The least expensive deal I'm seeing at the moment is for the Linksys WRT54GS-RM @ Mwave ($25 shipped, although recertified):
http://www.mwave.com/mwave/SKUSearch_v3.asp?px=DS&scriteria=AA97201
My personal preference is the ASUS WL-520GU @ Newegg ($35 shipped, after rebate):
http://www.newegg.com/Product/Product.aspx?Item=N82E16833320023
Again, the above require dd-wrt (or you could use
tomato too) to gain bridging capabilities.
OEM Solutions:
If you don’t want to deal w/ third party firmware (many ppl don’t), the best deal I know of at the moment is the ZyXEL WAP3205 @ Newegg ($43 shipped, after rebate):
http://www.newegg.com/Product/Product.aspx?Item=N82E16833181119
Has been as low as $31 shipped/after rebate in the past, so a bit high priced at the moment. But compared to most other bridges, still a lot cheaper, and you get a lot of features. Wireless N, WDS bridging, wireless client bridging, wireless repeater bridging, two LAN ports (presumable extendable w/ a switch), even multiple SSIDs for private and public access. Not that all those features would be applicable for your needs, but should you decide to use it in some other capacity later, you have a lot of options.
Anyway, as I said, I use dd-wrt compatible routers and wait for the best deals. Sometimes I’m able to get them for $15-20, but that takes some patience. Personally I believe the best value is the WL-520GU. Brand new, terrific w/ dd-wrt (or tomato) installed, exceptionally strong signal for its class, USB port, will accept all but the largest dd-wrt firmware (larger == more features), etc.
Or I suppose you could grab another WRT54GL if you found a good deal on that unit and install dd-wrt or tomato.