How Do You Arrange Your Books?

Ok, here's the deal: I have twelve bookshelves in my study and I'm pretty much out of space. They're, for the most part, full. When I get a new book and then try to fit it on the shelf, I have a hard time finding room for it without transferring other books on other shelfs (to keep them in order). So I'm considering a reorganization of my library to make it easier.

I currently have the following sections in my library:

1. Commentaries
2. Bibles and Greek Helps
3. Systematic Theologies and Dictionaries
4. Current Resources: Books I currently refer to for my current preaching and writing tasks; these are culled from the other sections, then put back.
5. Theology: These are put in the order that systematic theology is typically done.
6. Favorite Authors: Books by Piper, MacArthur, Sproul, Stott, and Lloyd-Jones
7. Biographies
8. History
9. General: in alphabetical order (this is my catch-all category with everything from The Reformed Pastor by Baxter to Dare to Discipline by Dobson.
10. Attractive Sets: think sets like "The Works of Benjamin B. Warfield"

How have you organized your library?