I save pretty much everything, i.e.plastic bags, bottle caps, glass bottles, coffee tins, bread tags, etc., pretty much anything that could be used for some sort of crafty purpose. After awhile I amassed quite a collection of beer caps. Last winter I created a mirror re purposing an old IKEA mirror into a bottlecapped mirror hot gluing the bottle caps and then later grouting it. I gave it to my beer loving roommate for Christmas and he loved it. Lucky for my its hanging in a shared living space so I get to look at it for a while longer.
This essentially wiped out my bottle cap collection for awhile, but I finally decided I had too many again and moved on to the next project.
I needed art for my bare living room so I used my many red-hued caps to create a heart shape on particle board and then filled the edges with mostly green, siliver and black caps. I still need to figure out a way to hang it but for now it leans against the fireplace.
I really love how it's a mosiac that from a distance doesn't scream bottlecaps or that perhaps we drink too much beer. Between these two projects only one of the caps was a soda cap...