Ben has a great tutorial on setting up a Dynalink RTA1320 or RTA1335 in half bridge mode so that you can have a world routable IP on a separate router (ie, a Linksys WRT54G). I have pretty much the same setup as Ben – the only difference is that I have a Dynalink RTA1335.
I can highly recommend these Dynalink products. So far I haven’t had any problems and I’m surprised at the quality of the firmware – far better than products from much bigger companies (ie Linksys, D-Link, etc). I can also highly recommend the Tomato firmware for the Linksys WRT54G wireless router. I used to run DD-WRT and was reluctant to move to Tomato because DD-WRT was quite good. After having moved though, I’m wishing that I had done it earlier. Tomato does everything that I need and it does it well.
One particular feature that I can’t live without is the bandwidth graphs in Tomato. There is also a feature to save the data usage logs to an SMB share so that if you have to restart your router, historical usage data can still be shown. Another feature that I’m quite happy about is the ability to force clients to use only WPA2 + AES to connect to the router. I ultimately want my network to be as secure as possible and forcing clients to use WPA2 + AES is a good way of doing that.