You can use bookcases as divders and for storage, and you can turn a tall, narrow bookcase on its side. There are also floating shelves, though I don't think they're very efficient, and I removed them from our new house and put a cabinet there (in the bathroom). There are some spaces where they may be useful. For more ideas, check out this webpage: Organization Basics: Shelves Home Made Simple
Sparkle note: If you drag a treat from the box, and click on it again, Sparkle will jump up and catch it!