I just upgraded my GPU to a 7990, so my old 580's just gathering (even more) dust atm.
I'm selling my ASUS GTX 580 Direct CU II (http://www.techpowerup.com/reviews/ASUS/GeForce_GTX_580_Direct_Cu_II/)
It's in good condition, never been over volted, runs cool, been through a few stress tests and come out the other side laughing. Still runs pretty much anything that isn't a poorly done port at max with 2x AA @ 1080p. I only upgraded because I'm planning on getting myself a 144hz monitor with the money I get back (and a bit I have saved).
Postage will be from Umina, NSW (2257) or if you're a coastie, we can talk about pickup (and I'll refund postage in person / via bank transfer / whatever).
Auction started at $100, buyout is $200. Registered parcel post + signature for postage. Please make sure you double check the length of the card and your PSU for compatibility. It's a long, thick card (3 slotter) and takes 2x 8 pins. Min recommended PSU would probs be a 600w/650w.
::EDIT:: It is dusty. I would clean it, but I honestly don't have the time or the can of compressed air. It's not SO dusty that it's affecting the heat of it though, it still runs well within safe temps even during hot summer days.
Also, I've confirmed it works as of just yesterday. It has been sitting in an anti-static bag since, so it's pretty much as close to 100% guaranteed as possible (because nothing is certain)