Here are a couple search results, formatted with links:
The Griffin iMic (USB-only, requires an RCA to 1/8" adapter, $35)
Formac Studio DV (Firewire, also does video, has RCA connectors, $250)
FireWire 410 (Firewire, bus-powered, in/out, MIDI, $400 (on sale))
The MBox (Audio in/out...