I have had success selling items on my local craigslist, but as nxstep warns... just beware of scammers.
Even though they are new, unfortunately you won't get full market value for them. Before listing them for a set price I would suggest doing a bit of research for similar CPU's/motherboards and see what they are selling for. Based on that you should be able to set a price that is reasonable.
If they are still boxed/unopened I would say you may be able to get 80% of what you paid, if they are opened probably a bit less than that.