Marcus Blankenship and I wrote a follow-up piece to our first article, mentioned in Discovery Projects Work for Agile Contracts. That article was about when your client wants the benefit of agile, but wants you to estimate everything in advance and commit to a fixed price/fixed scope (and possibly fixed date) project. Fixing all of that is nuts.
The next article is Use Demos to Build Trust.
That post prompted much Twitter discussion about the purpose of estimates and trust. I'll write a whole post on that because it deserves a thoughtful answer.