BCB picked up a vest from Circa Vintage in Melbourne last year. He was hoping for a full three-piece suit, but nothin' doin', so he bought a complimentary vest (powdery blue-grey suit; commodore blue vest). And he's been wearing it a bit on its own, too.
This post over at GreenShoesBride shows off the vest-without-a-jacket thing quite nicely. I like it. I think it could work well with a short dress, non?
Also, there is a gorgeously intellectual thread on appropriate wedding attire over here, at the London Lounge.
PS: Sorry for the lack of pictures. You have no idea how many *uncool* grooms in red or gold rental tux vests there are out there.