Advice on biking to work?

Now that I'm recovered enough from my knee-related fun over the summer, I'm planning to start bicycling to work at least some of the time. One flaw in that plan is that I do not, at this time, own a bicycle. In fact, I know next to nothing about what to look for in a bicycle: the last time I was shopping for one, I had very different needs and expectations (and hey, maybe bicycle technology has changed in the past fifteen years). So I put it to you, blogosphere: what kind of bicycle should I buy (and does it matter where I buy it)?

A bit more information: I live about 2.5 miles from work. I have my choice of riding to campus on a moderately busy street (Arrow Highway) or on a convenient bike path that runs right behind my apartment complex (most of the way, anyway). The route seems basically flat, though that perception could change once I'm riding rather than driving. I'm in decent shape apart from the knee thing (and my physical therapist tells me that bike riding would be good for me). I expect that most of my riding will be done during the day or early evening (but during the winter, the sun might certainly have set before I head home). I don't foresee any major off-road biking in my future. If there are other significant details that I haven't thought of, let me know!

Once I've picked a bike, what else should I make a point of doing or having done or buying to be set to go? (I don't know what happened to my old helmet, so I know that I'll need to get a new one.) Any advice from others who have tried this sort of thing?

Love in the Harry Potter books

Between the time that I moved out to California and the time that my classes started last fall, I re-read Harry Potter and the Half-Blood Prince and came to a surprising realization (that I'm reasonably sure must be true): Snape loved Harry's mother Lily. That idea apparently isn't news to die-hard Harry Potter fans (at least since that latest book came out), but it was a new realization to me (and I was quite proud of it at the time; I just never had time to share it after I started teaching).

I won't go into details about how neatly it makes the story fit together, but it does fit in with one of Rowling's oft-repeated themes: love is the one power that can overcome evil. The rather curious conclusion, though, is that it doesn't seem to matter what sort of love. Want to defy Voldemort's power at its worst? You can always rely on love, whether it's the unquenchable, selfless love of Harry's mother for her son, the unwilling, resentful love of Aunt Petunia for her nephew, or the creepy, stalker love of Severus Snape for Lily Potter.

Suddenly, evil doesn't seem like much to worry about.