"By now, you probably know that upgrading the near-legendary
Linksys WRT54G series routers with free, often open-source firmware
is one of the best bargains going. Replacement firmware typically
offers a plethora of advanced router and firewall features rarely
found on sub-$100 hardware.
"DD-WRT, a free, open-source firmware coded and distributed by
'BrainSlayer,' has emerged as one of the leading, most powerful and
also user-friendly firmware replacements for the WRT54G series.
DD-WRT is available for an increasingly wide range of routers
besides the WRT54G, including models by Asus, Belkin, Buffalo
Devices, Motorola and Siemens..."