eBay. Seriously, there are things that will sell there that won't anywhere else, mainly because of the global marketplace. But I fully agree - I'd like to see a better competitor come in and wipe the 'Bay off the face of the earth.
OfferUp and Facebook Marketplace are ideal for flippity-dippity type bikes and other things. But never the specialist stuff.
C&V Sales is OK, but slow unless you have something desirable. Couldn't give away a '51 Raleigh through it, and I've had a decent repainted PX10 up for trade for ages. Can't beat the clientele though
-Kurt