Groupon, a deal of the day website. Today I signed up.
Each day, Groupon offers a deal that will save you money at a local business in one of almost 100 different cities. After you sign up (which was a very easy process), you get daily a email notification of their deal of the day. If enough people join that day, everyone receives the discount. However, if they don't get a minimum amount of interest (the "tipping point" ) the offer is canceled. I've been assured that rarely happens; as a matter of fact sometimes the discounts are subject to quantity limits and they run out.
Unlike some other discount and coupon sites I've used, the deals at Groupon don't seem to have too many hoops to jump through. I don't know how many Groupon deals I'll be interested in, but from now on I'll get to decide each day!