I have a TON of unmounted stamps and, of course, my collection is ever-growing! My goal this month was to get them more organized. I found these great little bins from Cropper Hopper at my local Archivers. They come with plastic index cards that your unmounted stamps adhere to. I attach the sheet with the images to the card and then stick the stamps on and label the tab with the name of the set! I have several bins and divide the stamps by company - I have one bin divided by theme for my misc company stamps.
I store them all on shelves in one of those kitchen towers.