I have never heard of tapestry crochet but I checked out that website mentioned above and there are quite a few videos there about it. It looks like it's just regular single crochet using a charted design, much like knitting a design into a piece. You carry the unused yarn across, stitching over it, until you need it again, then you pick it up and drop the other yarn.
I especially liked the video where she showed how to work only from the front of the design so the design had a definite front and back. I'm not sure I could crochet from left to right using my left hand though! I am so NOT ambidextrous!
Anyway, if anyone out there makes anything using this technique, please post a picture here so we can see it. I'd love to learn more about it.