Daily Deal Sites
Group coupon sites are becoming the new trend these days. They seem to be popping up all over the place, and having local offers for most major cities. The way that they work is this: the business offering the deal sets a minimum number of people that must buy the deal before the deal will be valid. There is not usually a maximum number. Once the minimum amount is reached, the deal is valid, and the page will tell you if the deal has been validated yet. The page will also tell you the details of the deal. Many of them have a certain time limit in which you are allowed to use it. Some will be valid only on certain days or times, so be sure to read the fine print before purchasing anything to assure that you will be able to redeem it.
Here are some of the sites that exist. New ones are popping up all the time, it seems, so I will try to keep this updated.