I buy small pieces of art when I travel to big cities. There are often some nice little works sold directly by artists on the streets--near train stations or museums or parks, etc. Just look for things that are more original.
I think a lot of this is also up to you and your eye.
Have you considered making some of your own? I have a good friend who does some nice things just through photocopying old film images (or printing) and re-sizing, then framing. He's not an artist at all, but he likes nice works.
Finally, the best way to find good, less costly work is to befriend artists. Sounds ridiculous, but if you go to opening shows and meet the artists, it's often easy to get to know them. Most aren't looking about at those events to sell, but rather, they're getting toasted off their asses.