Where do you sell your old stuff?

Ebay for sure. It's hit and miss and I've had some really horrible sales performances, but equally some decent buys too.

If you have anything that is a known brand, you'll do a lot better. Also, if you own what was once a top-range part, you will still get decent cash for it now - far more than what it's actual performance is worth. I see Q6600's, E6600's, 6000+'s, 8800 ultras etc selling for stupidly high prices every day.

try everything, first one you get a good deal on, do it
i sold my old gaming rig to a friend for like $100 undercost (im a nice friend, plus we play many games together so he needed a good system)

You might be able to get more by disassembling your PC and selling the parts individually on e-bay.

To sell the complete PC, try craigslist first.

I part my old builds out and use the parts for charity jobs.

branded computers should move pretty quick on ebay, custom builds you'll most likely make more parting them out.

Mostly Craigslist, but if you want the maximum amount do a ebay auction.

I sold a 8800GT for $100 just 2 months ago.

There was a guy at my workplace who would buy my old stuff, but he retired a few years ago so now I just collect stuff, to the point where my wife insists on my recycling it.

Anybody wanna buy a gen-u-wine Pentium 150MHz system oc'ed to 166 MHz?? Plays Solitaire at 60 fps!!

Overclock.net seems to have a pretty robust selling/trading forum going on. The only problem there is that you have to accumulate a certain number of rep points before you can post a for sale ad.

Do like I do and sell on Kijiji. You will not have to touch your hold computer to sell component by component. You also don't have to try to figure out a way to ship your whole PC or have damage during shipping.

You can also sell a little higher because the buyer don't have to pay for shipping charges. I found a buyer after one week and got pretty much the price I was asking.