I have the following in my wedge under my seat, so I never have to think about it:

spare tubes (I need two - two different sized tires)
a tire lever
tiny patch kit
tiny multi-tool
lip stuff
tiny golf pencil and a folded up piece of paper

I have a pump with a gauge mounted on the frame, so that's always with me. My road ID is attached to my shoes, so I always have that, too. My sunglasses, helmet and gloves stay with my bikes when I'm not riding, so they are always right there ready to go.

When I go to ride I grab ID, cash, cell phone, water & maybe food (depending on the length of the ride)...oh, and a cue-sheet or map of the route since we are still relatively new to the area and exploring.