Appropriately enough, stonetools, I'm interested in pre-history, primarily UK & Europe, but any is of interest.
My problem is not many works in this field are available e-wise.
I have found some interesting, fairly esoteric, stuff in Gutenberg, Philly, and Baen, one fascinating piece on prehistoric fishing, which was fascinating, I have to say.
I am aiming to compile an itinary, spread over a few years really, of sites - anything on the Orkneys is a must have !
But an excellent idea for a thread/topic.