All the above is great advice.

A couple of posters including our very brilliant Rainman and very knowledgeable JohnE suggest using older road bikes from the 1970's or so.

I agree for two main reasons:

1) The old wheels @ 27" X 1.25" hold up better to the daily stresses of cracks, bumps, and potholes than newer 700 cm X ~23 cm wheels.

2) Daily commuting really takes it's toll on a bicycle. No matter how strong the bike is, frequent maintenance will be required. Commuting is especially hard on the wheels. Most serious bicycle commuters I know do their own maintenance due to convenience, and perhaps cost. At this point in time, spare parts can be had for nearly nothing by cannibalizing old discarded bicycles.

I also liked Pete's suggestion about carriers. That was fresh.

Welcome to the wonderful world of bicycle commuting. EVERYONE benefits from you choosing to bicycle rather than drive an automobile so be diligent and keep it up!