Through a collective buying process, Groupon, a national phenomenon that launched a Denver site last year, is able to offer a new deal from a local business every single day, which might vary daily among discounted restaurant meals, dog-training classes, exercise sessions, lube jobs, spa services and more. But it all hinges on the level of participation: If enough Groupon subscribers sign on for the day's deal, it's theirs for the taking; they can buy the deal online and print the Groupon voucher online. If not, well, try, try again.