Since I'm posting this so late at night, I'll probably repost for the benefit of people tomorrow morning. However, if you're up now, you should take advantage of this.
Currently, Microsoft and EBay have a deal going on. If you go to live.com and type in something generic into their search engine ("watch" works), one of the first results that will pop up will be an ad for Ebay, and you'll notice a little button that says "Live Search Cashback"
Click on that, and you'll go to eBay, but you'll now notice that there's a special tag at the top of the page that says "Microsoft Cashback: 25% off".
(UPDATE 2: The percentage you get off is tied to whatever search term you use at www.live.com. Typing in "SNES" got me 25%. It might change though, so play around until you get a % you like. )
For the next 60 minutes, anything you buy on Ebay with Buy It Now, Microsoft will give you back the % discount straight into your paypal account shortly after your purchase. It's that easy!
This is great for a lot of video game stuff that has the buy it now; it's basically just a free discount. Some unscrupulous people have set up little schemes, like one guy sold his brother a $999 fan and they pocketed the discount, but that's probably illegal so I don't advocate anyone doing that.
If you're looking for cheap games though, this is a great deal.
You can read the official terms here