(above via: here.) Instead of buying a new bookcase, opt for a thrifted one or keep the old one you already have. Give it a fresh coat of paint and either paint the inside or line it with scrapbook paper or wallpaper. Don't overload the shelf with clutter---let the pattern or paint get some attention.
(above via: here.) For a simple, studio-esque solution... prop open a ladder and insert some long planks of wood. Just make sure you don't put something too heavy on one end.
(above via: here.) For a more rustic look, choose a worn wooden ladder and add industrial touches like metal and vintage wire.
(above via: here.) If you are handy with a hammer and nails... or can manage to coax a handyman into helping out, turn one of your nooks into a bookcase with wooden planks. Avoid doing this in a dorm or campus apartment though---you might lose your safety deposit.
(above via: here.) Crates can exude vintage, rustic cool. Just make sure they're a nice dark brown or painted a uniform color and you'll have a cubicle-like storage unit.
(above via: here.) Scourge antique shops and thrift stores for boxes and drawers in different sizes and shapes. Paint them all one color... like a gorgeous turquoise. Line the backs/bottoms/sides with wallpaper or scrapbook paper. Stack 'em on top of each other and accessorize.