Getting Things Done by David Allen - This is a personal productivity system that encourages capturing all "projects" and being intentional about what the single "next action" is for any given project.
User Story Mapping by Jeff Patton - Honestly I did not read all of this and I probably should. However, I know this was very influential for people that I've worked with.
Kanban Development Oversimplified by Jeff Patton - This blog post does a good job of summarizing Kanban ideas in the context of Scrum and Agile.
Growing Object Oriented Software Guided by Tests by Nat Pryce and Steve Freeman - This includes a nice overview of an "outside-in" approach to software development using tests. The concept of a "walking skeleton" has been very useful for me.
Dreaming in Code by Scott Rosenburge - It's been a while since I read this but I know it covers things like "Mythical Man Month" in a story driven way.
The Agile Manifesto - That old thing, but really the 12 principles are the good part.
The Failures of Intro to TDD by Justin Searls - This, like GOOS, shows how we can use testing to build top-down or outside in.