The versatility of these routers keeps amazing me. As it turns out, they are also used to control robots. Two examples can be found here and here. Although they both use linksys routers, they use OpenWrt as their OS:
There is also a Canadian supplier of USB-based control and sensing boards, Phidgets Inc., which are apparently compatible with Asus wl500g routers. They provide motor control (including servo- and stepper-motors), analog sensors, RFID components etc. These components are fairly pricey, but look interesting for someone prepared to spend some money on building a robot.