Originally Posted by nmanhipot

This may seem like overkill to some, but I ride through several commercial and light industrial areas and have used everything in my kit multiple times. Below is a list of what I carry while commuting:

Two tubes
Compact pump (to be replaced next week with a Park frame pump)
Two CO2 cartridges
Park tire levers
Tire boot (for really bad days)
Emergency patch kit (for really, really bad days)
Universal tool
Compact first-aid kit
Quick Link
Cash

In the car and at home I keep a tire, tube(s) and CO2 cartridge(s) to replenish the flat bag, lube and rags. If you've got room for it, a lightweight folding tire is nice to have if you hit something really hard.