Strange timing on this one. I was out for a ride in Girona today (it's beautiful here) and broke my chain doing 30 second sprints. Thankfully I had a chain tool and a friend had a power link.
I got back home, catching up on messages and a group member had sent me a message asking what he should include in his saddle bag.
Feel free to add to the list. Here's what I think is important:
Pump, tube x 2, levers, multitool (with chain breaker), power link, tyre boot, valve core & remover, zipp ties.