In seat bag for any ride:

1 spare tube
1 patch kit
1 CO2 adapter
2 CO2 cartridges (the big ones)
2 tire levers
1 multi tool (which includes hex keys, philip and flat screwdriver, more tire levers, chain breaker, and other stuff) and the diagram explaining the tools I never use on the multitool, in case I need something that I can't recognize.

I should add a $20 bill in there.

In my jersey pockets:

If it's a winter ride, another spare tube and another CO2 cart, and another pair of gloves
A spare pair of gloves
Whatever food I think I'll need, + 1 unit for the eventual bonked rider I'll meet

I also have a frame pump with a pressure gauge.

And two water bottle cages with assorted drinks (usually water + lemonade if a long ride).