Thanks for the little tip, never would have thought of it
I have been trying out my new-used backup/multimodal/winter-beater bike recently. It has none of the storage and hauling items on it, so it is light enough for me to heave onto the bike rack on the bus if necessary. I like to cover the seat with a plastic bag while it is parked at work, in case of rain. If it does rain (as it did once) I don't like to put the wet bag into my nice new backpack. What to do? What someone suggested, just in passing in a thread on another topic: stuff it up under the seat.
Brilliant in its simplicity.
By the way, I saw at the LBS a bike seat with a little storage compartment built into it. It's one of those nice wide "old man" seats, so I might have to look into it.