Owner of a Linksys WRT45G router will be pleased to know that sveasoft, builders of really good firmware for this device, have publicly release the Alchemy firmware package. Until recently, this was only licensed to subscribers (of which I'm one :-)).
Now they have started a new branch (Talisman), rewriting it to be modular, so you can choose the features you need, and still leave enough mem available to keep your router happy.
So to get the free, open source, alchemy version of the firmware, get it at Sveasoft downloads at linksysinfo or at www.wrt54g.com