Very Large Rocks: Is there a market?

[def90]

Yes, I would start by contacting local landscape companies or local stone suppliers just to get an idea of what you have and what they are worth in your locality then decide how to sell them.

You could build a hell of a retaining wall out of them or split / cut them in to smaller blocks. Who knows, depending on the quality of the stone they could be used for carving as well.