...just in case anyone might find it useful, recently published by NIJ:

Investigations Involving the Internet and Computer Networks, DoJ Jan 07
Contents

...Technical Working Group for the Investigation of High Technology Crimes

Chapter 1. Introduction and Investigative Issues

Chapter 2. Tracing an Internet Address to a Source

Chapter 3. Investigations Involving E-Mail

Chapter 4. Investigations Involving Web Sites

Chapter 5. Investigations Involving Instant Message Services,

Chapter 6. Investigations Involving File Sharing Networks

Chapter 7. Investigations of Network Intrusion/Denial of Service

Chapter 8. Investigations Involving Bulletin Boards, Message Boards, Chat Rooms, and IRC Listservs, and Newsgroups

Chapter 9. Legal Issues

Appendix A. Glossary

Appendix B. Domain Name Extensions

Appendix F. Examples of Potential Sources of Evidence in Network

Appendix G. Sample Language for Preservation Request Letters

Appendix C. Accessing Detailed Headers in E-Mail Messages

Appendix D. File Sharing Investigative Suggested Checklist...