Wow! Monoprice.com is one of the best sites I've ever ordered from. It has hobbycity pricing with RCM store service! I just ordered $28 worth of ethernet cable, adapters, and a wireless usb card. It arrived two days later like it did last time.
The cable is so cheap. A 10' ethernet cable costs under a dollar. A 50' costs under $5. A 75' is under $7.50 etc. Monoprice.com is the place I would go for almost any wires or adapters. The also have some hardware, Home theater stuff, switches, and ink.
Another great thing about monoprice is the quantity discount. On every item I've seen you get a discount for ordering more then one. They also have some big rolls of some cables, including ethernet. My friend has a 1000' roll of cat5 cable which set him back only $62.60.
Just thought I'd share this site with the rcm guys if you don't already know about it.