Originally Posted by
buzzman
That day you work late, barely slept the night before, hardly had a minute for lunch and you get out onto the bike into the fiercest headwind you've ever encountered and suddenly it feels like you're on an Arctic adventure and all you really wanted to do was get home and have a cold beer and watch tv.
Were you following me yesterday?
You should always have a flat repair kit at a minimum, and a spare tube if you can. A flat repair kit consists of tire levers, patches, patch glue, sandpaper, and some way to reinflate the tire (I use CO2; some people prefer pumps). You can get little bags that attach to the seat post that will carry all this nicely.
I also recommend a cell phone. You never know when you'll taco a wheel or get a really bad cramp and need a ride home.
I also carry a small first aid kit, water, clothes, etc. Other people carry other stuff. You'll find what works best for you.