What do you pack onto your bike?

What do you use your bike for (commuting, races, fun, etc.)? What do you pack onto your bike? What accessories do you like to have attached on? From the basics (various repair tools/kits for the bike itself), up to any specialty items or home-made items that you prefer to use for various types of trips.

For commuting, a rack trunk with a change of clothes, lunch, pump, tubes and patch kit, basic tools (allen wrenches, small screwdrivers), reflective vest and leg bands in case i have to work after dark, light w/ spare bulb, cell phone, water.

For weekend ride, pump, tubes and patch kit, tools, cell phone, money and water

For commuting and fun, I carry a pretty sizeable bag everywhere. it helps me get in shape and im alway prepared, its the boy scout in me. i ALWAYS carry:

-3 rubber bands
-some aluminum foil
-a rain jacket
-a lock
-a water bottle
-tea bags
-lighter
-pen and paper
-spare tube
-CO2 inflator, steel core tire lever
-2 trashbags
-a knife
-chopsticks
-basic bike tools
-some candy
-disposable camera
-basic first aid kit
-small LED light
-plastic mug
-collapsible baton

I have a rear rack and pack as I dont like backpacks. I usually take off and ride for 6 hrs or more at a time. I take the wedge pack off my mountain bike cuz its got all my tools in it and put it in the pack main compartment along with a liter insulated bottle of water/ice. I also throw in a 20 oz gatorade in there. In the small compartment on the back of the pack, I carry bandaids, powdered electrolyte packets, sunblock, lip balm, a spare tube and my keys. On top of the main pack compartment, there is a zip compartment where I carry a multitool for quick access, air gauge, small bungee cords, digital camera, mp3 player, maps and money. The top of the pack has a bungee cord system to strap in raincoat or shedded clothing. The side of the pack has a cell phone pouch. On my handlebars, I have a mount for my Garmin GPSmap76CSx. I also have a frame pump on the bike. Over the years this is about the minimum I can carry and still feel prepared on long rides.

Good question.
Depends on where I am going and the kind of bike I am using at the time.
Sometimes I carry nothing but mi bike (Short commutes)
On other occasions I might tour for a day or two. The load gets bigger, but as small as necessary.
Most of the time I carry with me:
Basic tools, inner tube in case of puncture,
Lights (front and back) Never ride without them in the dark.
Reflective vest (If i know I will be riding roads with traffic or when dark).
Rains suit (well not if I am sure it is not going to rain).
A Lock
A mobile phone.

I pack as light as possible. For multi-day trips, I pack 1 change of clothes. Sun screen. My OCD directions.

This is in addition to:
1) credit card, for those hydration/anti-oxidant replacement stops at Stewarts.
2) Spare tube
3) Patches for smaller punctures
4) frame air pump
5) Shirt, necessary apparel for entering Stewarts.

If I'm going for a long ride on my road bike I only take the basics- bottle of gatorade, tin of tyre weld and that's about it. I always fit a mirror to every bike I have which is something most cyclists don't do but from a safety viewpoint I would recommend it. If I'm commuting I take a padlock, spare tube, tools etc.

I performance ride and race - it's all fun to me. Normally I pack a water bottle only.

Dang otto_rax you carry more stuff on you bike than I did in the moving van when I bought my new pad!