Hey the following 2 products are a must have if you are serious about furthering your skills as a drifter.
The Drift Bible - by Keiichi Tsuchiya (The Drift King)
This video shows you how to preform 6 different techniques: E-braking, Shift-locking, Power Over, Braking, Feinting, and the Lift Off. Tsuchiya also shows you how to take advantage of your car's weaknesses whether it is under-powered or under/oversteers. This is an excellent video and I highly recommend you watch it!
How to Drift: The Art of Oversteer - by Paul Morton
This book is an excellent guide to both the driving technique and car setup required for drifting. This book contains a large amount of pictures as well as very detailed descriptions of the skills. What is great about guide is that it includes a section on how to transform a budget car into a drifter by giving you detailed chasis, suspension, and engine modifications.
Enjoy!