MRHELLO, take a drive and look for roads that lead into undeveloped areas. People back up to the curb and dump concrete chunks, blocks and bricks all the time. I have been cleaning up just such an area for quite a while. If you can get ahold of the landowner, they may be glad for you to take whatever you need or they may tell you to stay away because of liability issues.

In the area I get my materials from, I have been approached by cops several times, so they are patrolling for illegal dumping. What blows their minds is the fact that anyone would want to take the stuff instead of dumping there. For some self-defense, pull out your phone and take a picture of your empty truck bed when you pull up, as it'll have a time stamp in the properties of the photo. Usually that's not a problem.

The property manager of the adjacent facility drove up to me and said, "Well, this is a first!" I told him what I was using it for and we got into an extended conversation about pond management.

Also, check the "free" section on Craigslist...most people will give you anything they feel has no value, or requires manual labor.