if you want to be creative use beads. bring your thread up through the fabric, through the hole and back into the fabric. you can also use little sticks (i have done that - very hippy looking). just come up, wind around the stick or twig and back down, a few times. make sure the stick is rough.
buttons don't have to be buttons. a really GREAT thing to use is old keys. they look fantastic. i made my dd a vest that closes with old keys. if it wasn't gone, i'd post.
nut, bolts, springs, etc. visit the hardware store. anything that goes through and hangs down (ooops!).
you can even use safety pins by slipping them sideways through the buttonhole. they're lots of fun.