http://www.monoprice.com
If you have a need for-
Home theatre cables
USB/Firewire cables and adapters
Speakerwire
Video/Audio switches
Network cables
This place is awesome. Prices seem to be less than half of competitors and they seem to have a large inventory.
Last year I bought all my home theatre cables from them (ex. HDMI cables for $12) and I just bought a firewire adapter for $10.50 (came with a cable and Ulead software too).