Left pocket: Food
Middle Pocket: Phone, $20, tube, valve extenders, CO2 doohickey, KMC missing link. All bound up nicely in a ziplock bag.
Right pocket: empty food wrappers (also acts as catch all for when I peel off arm warmers, jacket, cap, etc)
Saddle bag: bike multi-tool, tube, tire lever
And when I'm not racing I have this neat thing that mounts behind a bottle cage that holds up to four CO2 cartridges. I usually only take two (three total counting the one in my pocket). One for me, one for a friend, and one to prevent walking home. If we had any appreciable climbs around here I'd maybe be a little more conscious about the extra weight. Yesterday's ride was 50 miles 900 ft of elevation gain.
I've been lucky and only had three flats on the road. The first required a call home because my spare tube had a hole in it and no one had a tube with a valve long enough (hence the carrying extenders). Flats two and three happened on one ride. Had to call for a ride because enough time had passed that I got lazy and stopped carrying a second tube and valve extenders. Now I probably carry too much, but I'd rather be prepared since our rides can end up 30 miles from home and 15 miles from the closest town.