Woot.com sells one product each day. Does anyone know where they source their products? If it's overstock stuff or items that manufacturers want to get rid of, how would I get in touch with these manufacturers? Does Woot actually store and ship the products themselves or do they outsource that?
They are essentially advertisers, so they would go to a particular company and say "we expect we can move X amount off product if you can give us Y% off". This site suggests groupon made quite a nice deal on their GAP offer.
It's not necessarily overstock or items manufacturers want to get rid of, these sites need good quality product to be popular.
I would assume they don't deal with the logistical side of things as the business they sell for already does this, they are just a social front-end.
The targets for these sites are big distributors/manufacturers who have plenty of product to move.
If you want to build a site like this you are best to start small, work with those places that already spend a lot of money on advertising e.g. deals on pizza etc. and then work your way up as the traffic increases.