I sell mine on gumtree (the Australia equivalent of Craigslist).
Yep another strong vote for Gumtree if you are in Australia. eBay is officially on the nose now for private sellers.
Just had a look at Gumtree for the first time in years and was surprised by the amount of camera gear there. What's the drama with eBay? Is it the fees? I rarely sell things, but eBay has been my way of doing it in the past.
Gumtree is quite a good resource if you live in a city in Australia. I live in Adelaide, which has a population of about 1.2 million (so medium size city) and it has enough 'buying-selling or to-trade business / traffic' that it's worthwhile.
I have sold a few of my previous lenses on it - which were in good condition - and at a very competitive (ie fair) price. I wanted a no-fuss sale (my time is worth money too). Over the years I have bought items on it - eg 2nd hand ball-head (but not lenses or bodies). Just my personal preference, I prefer these items new - even if I have to import from USA & SE Asia (when I come across a good deal from those places).
There are also a few facebook pages, Australia cameras buy sell and trade (something like that) and 'Australia Canon buy and sell'. These are good, have decent moderators (eg price needs to be mentioned, and photos attached, otherwise they are removed.
On both these mediums - some people try to sell items at ridiculously overpriced amounts (eg more than I can get new imports, including shipping). They often say 'Best camera' 'Amazing' 'Quick sell' (eg when it's a 5 year old body with 80k clicks on it!)
But most people take a more reasonable approach...
I know the market well enough so I speak with authority and if people try to bargain me down, I indicate (truthfully) the number of other people who have contacted me about the lens, and I'm willing to wait for a 'reasonable price' not eg if I listed my lens at $400 and they offer me $250, I say... "No, $380 is the lowest I'm prepared to go. I'm expecting someone might also pay me $400 for it too"
All has worked good so far.