Well how the heck do you expect to sell it if eBay or Craigslist are too much of a bother? You can see if some of the Mac resellers will buy it or at least give you a trade-in towards store credit, I bet they'll offer you $100 for it.
The quickest and fastest is Craigslist. I just sold my 12in Powerbook G4 and iPad on there. Both devices the people e-mailed me, I called them back, met them at Starbucks later that day and got cash on the spot.
eBay, because of the wider audience, might net you more money. All you'll have to do is stick it in a box and ship it. If you use USPS, you don't even have to drive to the post office - just print the label at home and hand it to the postman.
BTW I got $250 for the Powerbook, so you should be able to get $300+ I think.