craftgrrl | Do-it-yourself shelving?

I want to make some custom bookcases for my foyer, since I'm running out of bookshelf room and I hate the pre-fab look of the particle board shelving sold at most office-supply stores and Target, plus I figured that I could definitely make shelves like that for a lot cheaper. I like the sturdiness of real wood, but also want to make more "mod" style shelves, like the stackable H-shelf or cubes. I checked on DIYNet and found a "built-in" bookshelf project, but I live in an apartment, so I don't want to actually mount the shelving to the wall, though, for sturdiness sake, I might do so since I have a baby who will eventually be toddling around them.

Has anyone here made bookshelves (whether mod-style or normal) before? What did you do?