I can tell you that I bought/read "USB Design By Example: A Practical Guide to Building I/O Devices," by John Hyde (ISBN 0970284659). It includes complete examples and a CD with all of the code on it. You can find it on Amazon.com along with several other USB tutorial books (including one by Jan Axelson that caught my attention). I can also tell you that reading the book was all I needed to be convinced that if I am ever going to add USB to any of my projects it's going to be with one of those chips like Michael mentioned.

Good Luck.