1982-ish Ron Cooper with the Rivendell Banana bag I move between my bikes for most rides. Bigbossman calls it my "steamer trunk," but it holds everything I might need on a ride, including the spoke wrench needed to get Mrs. Bigbossman home when a spoke broke on the cheap-ass wheel he got her.

(He doesn't tease me about quite so much any more.
I have a Riv Hoss bag on a Carradice frame thingy, too, which I use for commuting and hauling extra crud on my Paramount, but no pix of it in action. The frame thingy lets me use it on my saddle of choice (San Marco Rolls Titanio), which does not have the bag loops the Hoss (and Carradice bags) otherwise needs. The frame thingy also makes the bag instantly removable and put-on-able.