To your list I'd add lights. When I worked in a hospital, I remember most surgeries were scheduled early. That means riding to work in the dark. I'll also second the nomination for a mirror.

For tires, any good puncture-resistant road tire will do, although most of us have personal preferences. Cross tires--racing tires designed to run in the dirt, sand, gravel, and on grass--are generally not puncture-resistant and wear quickly in regular use on pavement. Their tread pattern too puts less rubber on the road.

Finally, join us on the Commuter Cycling Century Challenge (2010 thread linked) over on BikeJournal.com. The goal is 100 commuting days in the year. At two per week, you'll make it, no problem.