Kindle Organization

If you follow me on Facebook, you may have noticed my announcement last week that I appear to have run out of storage on my primary Kindle. Of course, all of my books and samples are stored in the cloud, so I can download them and delete them at will. The problem is that when I first started my Kindle library, I was able to sort my items into collections by genre and read/unread status. I probably have thousands of items now, which makes it impractical to keep my collection sorted. (I discovered recently that you can put items into collections through the Amazon website, which is easier to use than the Kindle. However, since you still have to assign items to collections individually, and the status isn't immediately apparent, it's tedious work.) So I keep unread items on my Kindle and delete them as I read them. However, I still add items to my library faster than even I can read them, so at some point, I may have to delete unread items from the Kindle, which means I'll forget about them.

Any recommendations on how to better organize my collection? If so, feel free to share them in the comments.