I've worn a fanny pack outside of my leathers for my wallet and phone. Kinda dorky though, but then I looked like a power ranger so it didn't matter that much.
I went all out and got the tail rack and Givi box for commuting, but before I did that I had a Cortech Sport tail bag, and was looking seriously at the Kriega waterproof packs.
Cortech:
Kriega