Oldschool:
Dan Kennedy & Bill Glazer (you already mentioned them)
Jay Abraham
John Carlton
Gary Halbert (RIP)
Younger guys:
Frank Kern
Eben Pagan
Mike Filsaime (former used-car salesman, he'll spam you to death
)
Jeff Johnson
Jeff Walker
Rich Scheffren
Probably a whole bunch more, both oldschool and younger ones I can't remember right off the bat. But many will just regurgitate what the above have to say, albeit with a twist on it.
If you want more pointers on whom to check out first and what to look for, feel free to hit me up on ICQ (1566665).