One step up from garbage scavenging is to shop garage/yard sales. If you have some vision then this may be another way to utilize your creative juices. I've found that this is another inexpensive way to find pieces to create art.
My sister was getting rid of two end tables in her garage sale and I was looking for end tables, so I confiscated them (free in exchange for my labor) and using a wood burner and some different size glass canister rims I etched shapes into the wood after putting on a primary paint color all over the surface. Then I painted inside the etched circles a different color and sealed the entire table with a clear varnish.
However, I decided I wanted a piece of glass to go over top of the tables for extra protection. I looked online and in stores for the correct size and shape of glass- which turned out to be very expensive therefore not an option. It turned out I didn't even need to be that patient- I searched craigslist as another option and within a day found the same end table with glass for $5 so I purchased it and then within in a week found another one for $8. The only problem was that I now had four tables and only needed two. To solve the problem I ended up using the same technique but different colors and used the two spare tables in my work office space which didn't really need extra glass protection.
Outcome: 4 usable unique end tables for a total of $13 and a few hours of labor!