1. The Original USB 2.0 specification released on April 27, 2000
2. Errata to the USB 2.0 specification as of December 7, 2000
3. Mini-B connector Engineering Change Notice to the USB 2.0 specification.
4. Pull-up/pull-down Resistors Engineering Change Notice to the USB 2.0 specification.
5. Errata to the USB 2.0 specification as of May 28, 2002 
6. Interface Association Des criptor Engineering Change Notice to the USB 2.0 specification.
7. Rounded Chamfer Engineering Change Notice to the USB 2.0 specification as of October 8, 2003
8. Unicode Engineering Change Notice to the USB 2.0 specification as of February 21, 2005
9. Inter-Chip USB Supplement Revision 1.0 as of March 13, 2006 
10. USB On-The-Go Supplement Revision 1.3 as of December 5, 2006 
11. Micro-USB Cables and Connectors Specification Revision 1.01 as of April 4, 2007
12. USB 2.0 Link Power Management Addendum Engineering Change Notice to the USB 2.0 specification as of July 16, 2007.
13. High-Speed Inter-Chip USB Electrical Specification Revision 1.0 as of September 23, 2007
14. Suspend Current Limit Changes ECN as of April 9, 2008 

Please check this site for any future updates to the USB 2.0 specification.