IKEA's Frakta bag (the big blue one) is handy if you've purchased a bunch of impulse items, and still pretty useful if you want to store stuff around the house. I'll admit that converting it into clothing hadn't occurred to me, but it turns out to be surprisingly easy.
At IKEA Hacker, Adriana demonstrates how anyone with a little sewing know-how can make the bag into a mini-dress, though it's self-evidently not a style that anyone could pull off. For a more practical bag repurposing, check out the messenger bag conversion.
Ikea blue bag halter dress [IKEA Hacker]