Besides books (see CategoryBooks), there are articles and pre-publication book drafts that are freely available. Check out these:
Driving Software Projects with Examples by Brian Marick
describes iterative development based on concrete acceptance tests and the collaborative give-and-take with the Product Owner.
"For the product owners, avoiding disappointment requires control. For decades, product owners have been told that control comes with knowing their own mind, expressing themselves exactly and completely at the beginning of the project, and otherwise keeping out of the way. That's silly. Think of pretty much anything important you do: driving a car, raising children, choosing a career. Would you really want to stake everything on getting those right up front?"
"Finding good programmers is hard because good programming is dependent on much more than just knowledge of programming language syntax. You need someone who, despite wearing striped pants with a polka dot shirt, has a good sense of taste in OO design. You need someone who is creative enough to find innovative solutions to problems, yet anal retentive enough to always line up their curly braces. You need someone who is humble enough to be open to suggestions for improvement, but arrogant enough to stand firm and provide leadership when they are the best person to provide it. How can you tell all this about a stranger by spending 30 minutes with them in a conference room?"
O'Reilly Open Books Project, free.
a paper on Target-Cost contracts for agile projects at Agile2005.