If you just mean prints then check places like Marshals, TJ Max, Big Lots and Burlington Coat Factory. They're kind of hit or miss places so you may have to check back until they happen to have something you like though.

art.com has a whole catagory devoted to abstract or modern. I found a home builder that was getting rid of ALL the art his decorators used to stage his model homes in my area. They had a big sale. VERY discounted. Then gave the rest away to family,friends,coworkers then Salvation Army picked up what was left. CL is now flooded with model home pieces for sale. :0)

Here is a link that might be useful: Contemporary art....

Pick up a copy of Dwell magazine and look at the ads in the back.

Here is a link that might be useful: Dwell magazine

Resale shops. I also found something very interesting once at Target! Mixed in with my more expensive items it looks expensive.

Our contemporary art collection got started in the 70s with an office closing -- we got several things for a song -- to our amazement, three of them are now quite valuable.

Other than those, we've just found things at local galleries -- fun to visit local places when traveling. I love the idea of supporting local artists.