IPv6 is designed as an evolutionary upgrade to the Internet Protocol and will, in fact, coexist with the older IPv4 for some time. IPv6 is designed to allow the Internet to grow steadily, both in terms of the number of hosts connected and the total amount of data traffic transmitted.

IP Next Generation Overview 
This papers provides a comprehensive overview of the IPng protocol and describes the work of IETF IPng working group. It was written by Robert M. Hinden, Director of Software at Ipsilon Networks.

IPng working group
Provides information on the Next Generation Internet Protocol (IPng). Includes an overview, specifications, presentations, and working group activities and documentation.

Yahoo!'s IPv6 page
Yahoo!'s directory of information and documentation for IPv6.

RFC 1752
Request for Comments document for the IP Next Generation Protocol.

The recommendation for the IP next generation protocol RFC
Request for Comments document on the recommendation for the IP next generation protocol.