depends on what I plan on doing that day.
Commuting:
rain gear
work shoes
extra tube/tire levers/pump/leatherman/allen key set
map
extra batteries for taillamp
lock
shopping:
extra tube/co2 inflator/tire levers
map
extra batteries for taillamp
lock
long ride, possible shopping:
two tubes/pump/tirelevers/leatherman/allen key set
granola bars or a sandwich
2 Extra water bottles
lock
map
Group ride (I'm sporting the spandex, so no pockets):
Camelbak MULE
lock
two tubes/tire levers/leatherman/pump/allen key set
cellphone/wallet/keys
map
2 gel packs
Pretty much I'm a fan of being equipped for anything.