Classroom Library Organization

My classroom library is a source of constant agony.  My first and second year, I looped from Kindergarten to First Grade.  My first graders knew what I expected and respected my books and our library as much as I did.  Last year, however, my students could not seem to keep the library in order.  I was constantly re-organizing and putting books back in the bins where they belonged.  I don't know what I did differently, or if it was just my class, but I think I'm going to change my library organization....again.

I'm going to keep a large bookshelf for units of study, such as Spiders, Ocean, Christmas, Jobs, Inventors, etc.  These books will be featured on a special shelf during that unit for the kiddos to browse through.  I'm going to keep all other books (Arthur, Dr. Seuss, non-fiction, etc.) in these baskets.  I found them at Target for $3.99 and they come in 4 colors- teal, lime, black, and pink.  I bought 7 of them.

I also have a leveled library for Independent and Guided Reading at the front of the room that my kiddos have access to.  So my question is...how do you organize your library?  Themes?  Reading Levels? Browsing Boxes?  I want to know!  :)