Originally posted by Otto
Check with your local hobby shop. He might take them on consignment.
Yeah but don't play the total RC noob or else he'll rape you, "Oh a Jett .50 engine... well ya might get $20 for it" kind of BS. Maybe consider asking him about the local club and contacting some members there. More than likely they have a newsletter that you can advertise the items in.
Another thought, once you find out what is there, is to go to Tower Hobbies website and maybe get an idea on how to price the engines/accessories.
If there are any 4-stroke engines or unstarted kits please contact me.

And yes, RC is a great hobby, be it planes, helicopters, cars, or boats.
http://www.towerhobbies.comhttp://www.rcuniverse.com (lots of ads... be patient)