actually that is a pretty general question...for intermediate no limit Lederer's More Secrets of No Limit Holdem is a good start,then World Poker Players Conference good seminar by Mark Gregorich on playing professionally and final tabel play by Daniel Negreanu, Phil Gordons is good and Annie Duke's Advanced Holdem secrets is the best advanced DVD, Finally whether you like Hellmuth or not his overall poker talent as seen in the National Heads Up Poker Championship is essential if you want to get better at heads up or are constantly finishing 2nd or 3rd in the sit n go's. I think each of the mentioned will take years off the learning curve.