Honestly, scavenge thrift stores, and hobby lobbby. I went to Hobby Lobby today and the clearance section had a bunch of cute decorating things/mirrors/frames/candles/youknow for 50-66% off. sooo cheaps. And those DIY links that Meg gave you are fabulous. I want that hula-hoop rug nowwww
also,
http://www.craftster.org/
and I get inspiration from Ikea, Urban Outfitters(the apartment furnishing things), and random catalogs/mags.
OHOH, and Craigslist free section, is awesome for finding random things. or if you live in a college town, watch dumpsters/trash can areas, for when people graduate/move. lots of good freebie scores.