One site that can help you with both (but mostly the latter) is SlickDeals.net - a collection of all the best promotions, rebates and other special deals from around the world, most of which are available online. Browsing it can be quite profitable at times, but you often have to look beyond the deals on the front page to get the ones that are right for you.
A few useful things I got today from the SlickDeals forums today:
$100 free for opening a savings account with Citibank (no deposit required, though with the current lending crunch I'm sure they'd appreciate one)
Excessively cheap prices on Pirate's Booty chips (which happened to be combinable with a $10 off $50 coupon MEAL1000)
500 free miles (plus mileage refresh) for filling out NWA quizzes (useful if you've not flown with them for a bit)
Here's one for Midwest FurFest, if it lasts: Never-ending pasta at Olive Garden - though if you're really hard-up you could probably just eat out of the con suite
One thing to remember: A big part of being thrifty is not spending money at all. Sites like SlickDeals can encourage you to go broke taking advantage of deals on things you do not actually need and will not use - so be careful. And always read the fine print. :-)