I quite like Tom Williams 'undeclared secrets that drive the stock market'. Its based on Wycoffs work. Its probably worth starting with Wycoff if you havent been there already. The little book he wrote under the psuedonym Rollo Tape is a good intro. DBPhoenix wrote some pretty good free stuff - search here and you will get to it. Theres a couple of others that escape my memory right now.
Cheers,
Nick.