I am a newbie commuter with only 22 miles to my credit. I am only riding home at the moment till I get in better shape and can reliably make the distance in a set amount of time.

I must say that the advice here is of great help to me in deciding what to pack for the trip.

Here is what I take with me so far:

1. Helmet
2. Safety vest- I am lucky and get them for free from work.

In the backpack I have:

3. Flat repair kit
4. Bike multi- tool
5. First aid kit- never leaves my pack!
6. Gloves
7. Sunshades/eye protection
8. Rain poncho
9. Water- trying to decide if I need my hydration bladder in the pack or if the water bottle on the bike will do.
10. Return home items- Lunch continer, dirty work clothes, etc.
11. GPS attached to handlebars to track average speed and milage.

Other than that I carry my wallet, keys and other such stuff in my pack as well.