Overstock's cheap on listings. I think on UBID, you have to be a certified business to sell there. I've tried selling there but you have to have a reseller's license. Would be nice to be able to. I've seen a lot of electronics sell on ubid for a lot higher than on eBay.
Yahoo's not bad either however you'll get a TON of scammers. I've tried selling car audio and found eBay has very strict rules on it.
Keep an eye out for ubid's mega auctions. I've gotten some good deals on fosgate amps from there.