Igor Ledochowski's product "Power of Conversational Hypnosis" is amazing.

Rintu Basu's book "Persuasion Skills Black Book" is very good.

"Trance-formations" (the original) is a must read as well.

That should be enough to get you started. Also, Dave Riker's language course is very good as is Ross Jeffries' New Jersey 1995 Seminar. Hard to find, but pretty good.