The AdWords Help Center now has a section for Keyword Insertion:
Dynamic Keyword Insertion
And there are 7 sub-topics there right now:
* How do I use keyword insertion? (tutorial)
* What is keyword insertion?
* When and why should I use keyword insertion?
* How does keyword insertion work with broad-match keywords?
* Will using keyword insertion affect my keywords' Quality Scores?
* Why doesn't my keyword appear in my approved keyword insertion ad?
* Why was my keyword insertion ad disapproved?