Running shoes (possibly with elastic laces)
Water bottle(s)
Water or sports drink
Sunglasses
Bike shorts
Jersey/other race clothing
Cycling shoes
Spare pack (including a tube, tire levers, patch kit)
Bike pump
Gu
Bike (someone actually left theirs behind a few years ago)
Helmet
Driving directions
Warm up clothing for before the race
Wallet, ID, etc.
Breakfast (~500-1000 calories 2.5-4 hours before the race)
Ibuprofen/inhaler/etc Extra drinks and snack food
Gas in your car
Towel
Could bring some cleaner clothes for after the race
Camera/cell phone/miscellaneous personal