Given that philosophy as practiced in academia is as much about creating arguments as about the ideas themselves, I suggest "The Philosopher's Toolkit" as a useful reference.

For what I'll call "hard philosophy" I put my votes for books by Hilary Putnam and John Dewey. As a rationalist seeking a solid basis for ethics in the physical world, I've found both authors quite instructive. Perhaps "Objectivity" by Nicholas Rescher belongs here as well.

There's a whole other class of what I call "idea books" and I've seen a few of them listed in the comments, too. Given the reading examples you mentioned, I'm assuming you're looking more at "hard philosophy" so I'll skip the other kind of suggestions unless you ask for them.