Daily Deal Mojo has a great post about doubling your budget with daily deal sites at Money Saving Mom. This is a must read! Then check out Daily Deal Mojo to read about all the daily deal site offers. I think these daily deal sites can be very helpful for stretching your budget, but I would caution you to set a budget for spending on them, or include them as part of the budget category they fall under. Personally, since these can be used for gifts, groceries, eating out...well, just about anything....I am making a budget category for them and I will filter a few dollars from my grocery, entertainment, gift budgets, etc. I am also considering taking any leftovers from the budget categories and moving some into Daily Deals budget, and the rest to savings. Also, do not forget to check Ebates (or other rebate shopping sites) to get your cash back on these purchases! You may want to think of devoting the cash back from those purchases into the Daily Deals budget line.
I think this can be a great budget stretcher, but caution you not to go overboard!