The new big thing in online shopping seems to be these collective trigger coupon web sites that are popping up all over the place. The largest player in this category is probably Groupon.com, which offers shoppers in 17 cities a daily, emailed deep discount offer that only kicks in if enough people sign up to use it. For example, a recent “groupon” offered a spa treatment that normally costs $120 at a local salon for only $50. The deal required that at least 40 people made the leap before it went into effect, which turned out to be no problem: 951 people bought the discount before it expired. The D.C.-specific version of Groupon can be found here.

And today we learned about a recently launched D.C.-based competitor, What’s the Deal DC?, that works much the same way. Today’s deal is a $20 gift card to Adams Morgan’s A Little Shop of Flowers for only $10 — but as of this writing, they are still 14 buyers short of making it happen.

No doubt in this economy, both business owners and shoppers are looking for a way to balance their budgets. Would you (or are you already) using one of these discount sites?