Here's all I carry for any ride > 20 mles.
Two tubes AND a patch kit. As was said above, sometimes you get N+1 blown tubes, where N is the number of spares you carry.
Pump or CO2 inflator.
Tire levers.
Chain tool - got me home one day when my rear derailleur cable broke 8 miles from home.
Spoke wrench - got me home when I broke a spoke 20 miles from home.
(It's been years since I needed the chain tool or the spoke wrench, but having needed them once.....)
Two bottles of sports drink.
1 PB and honey sandwich (cheaper than an energy bar and doesn't give me gas).
Cellphone, drivers license, health insurance card.
$5
Front door key
If it's a long ride, and/or a hot day, the $5 comes in handy to buy drinks and/or candybars.