I sell mine on gumtree (the Australia equivalent of Craigslist).
Gumtree provides you with free ads (sell, swap or buy) , and you can meet face to face (do this in a safe, public spot) to try / purchase, etc. I've had success in selling 3 Canon lenses that way in recent months.
I sold the lenses below what I got them for, but I expected that, and the reason I sold them for cheaper was:
- I had a LOT of use over several years
- they were not L lenses
- each lens had been superceded in more recent years with superior products (ie newer / better lenses available).
So I was happy with getting at least some decent money for them, but having a clear conscious I was selling them for a reasonable price.
Gumtree really worked for me!