Where (online or in LA/SoCal) to sell model kits?

IPMS Orange County has its monthly chapter meeting this Friday evening. You would have a ready made crowd there for you. We occasionally have people such as yourself who are not chapter members stop in and do the exact same thing. 

Here is the link to our club's website

http://www.ipmsoc.org/who-are-we/international-plastic-modelers-society/ipms-orange-county-ca/

Many people sell their old kits by renting a table at local contests and shows.  Sure, it costs a fee to rent the table or space, but there will be a lot of prospective customers hanging around, and no middlemen to soak up some of the price.

I know that this is an old post, but of you are still interested Pegasus Hobbies in Montclair buys kits. They have a fairly large collection of older kits and will buy them in large lots. 

Good luck!