Yard Sales - by far my favorite place to shop during the summer months. You don't always find what you're looking for, but with a little patience and hunting you can get some great deals on some great stuff! You can see my tips for yard sale shopping over at Active Fingers, and check out some of my yard sales finds here.
(serving stand - $0.50 from a yard sale)
Thrift Stores - a nice alternative to yard sales in the winter. Merchandise usually isn't quite as cheap as at a yard sale, but you know you'll have a huge selection in one place and that it will get updated often.
(bag made from a duvet cover - $4.00 from the thrift store)
Craigslist - nice because you can look search for specific items. I've found Craiglist prices to be generally higher than the former options, but it's nice to be able to shop from home and look for exactly what you need. And the prices are usually better than buying something new.
(crib - $50 from Craigslist)
Freecycle - my parents have gotten some really good stuff from their local freecycle network. I haven't had tons of luck with freecycle yet, but it's because things go SO fast. I don't check frequently enough so most things are gone before I even know they're there. But, if you're diligent, you can get some great stuff totally free.
Clearance Aisle - in all the places you normally shop. Most stores have at least a small clearance section and, while some things there seem to be hardly marked down at all, sometimes you can find a steal!
(drawer pulls - $0.30 each from Lowe's clearance)
How do you save money and stretch your budget when you shop for your home?