I just got some vintage bottle caps that i'd ordered from my favorite supply website (www.mantofev.com) and made some pretty cool earrings....go here: http://tinypic.com/o9rc to see them. this is the link, i'm not sure how to insert the picture into the message. sorry. There's kinda a glare but you'll get the idea.
all i did was hammer a small nail hole into the outer edge of the cap. these caps were already sort of "opened." when i use other caps, i usually use a pliers to pull each little "fold" or crimp out a little to sort of open the bottle cap up a little more...just me, i think they look better like that.
also, a quick little plug, or shout-out if you will...i'm selling some on ebay, if you're interested.