i swore by WRT54GL w/sd card mod for many many years (on dd-wrt, then tomato). jumped ship to an Asus RT-N16 recently cause i needed the wireless-N and gigabit switch. currently sporting the Toastman mod of tomato, Shibby mod is also good choice.
Toastman: http://www.4shared.com/dir/v1BuINP3/Toastman_Builds.html#dir...
Shibby: http://tomato.groov.pl/download/