MVP Scott Stauffer does a fantastic job of explaining what Kerberos delegation is, the issues it solves, and provides an extensive list of resources to close out the chapter.
This is the best resource I have found for understanding Kerberos and how to implement it. K. Brian Kelley has an excellent article on SQLServerCentral that is good, but not quite as in depth as this chapter. Scott lays out the process logically beginning with how and why he came to understand the process, taking you through what Kerberos is, what issues Kerberos delegation solves, and providing a business scenario that Kerberos will solve.
Kerberos is a complex topic which Scott makes simple in his section Understanding Kerberos Delegation. He explains SPN’s (Service Principal Names), permissions needed to work with SPN’s, and the tools you will need.
Scott very clearly takes you through implementing Kerberos from beginning to end. He includes great screen shots and code snippets along with explaining WHY you need to go through each of the steps.
Scott also included a section on validating your delegation setup using a tool called DelegConfig. This tool is run on the client and web tiers and will validate that Kerberos delegation is configured correctly and working.
Finally Scott provides 3 pages of resources to use to learn about and implement Kerberos delegation which includes: tools, blog posts, TechNet articles, MS Help & Support articles, white papers, and webcasts.
This chapter is really a one-stop shop for people who need to understand and implement Kerberos delegation.