I mostly commute to the office. The most common thing I forget is a water bottle, maybe three or four times a year. Sometimes I go back in the house and get it, sometimes not.

Next, about twice a year, I forget to bring fresh underwear and socks to change into at the office. But for the last few years I carry a spare pair of undies in my commute pack, and I keep spare socks at the office so I never have to spend the day in potentially gamy briefs. Why I don't keep extra undies at the office, I don't know, but there's a Target a quarter mile away, so I have that as a backup.

I often run banking and shopping errands on the bike at lunch. About once a year I forget to bring my wallet with me, so I have to ride back to the office and then again to my errands. Usually it's within three miles, so it's not too bad.

The only other thing I forget with regularity while riding is I forget where I'm going...or specifically, I forget to make turns if an errand it takes me off one of my usual routes. Sometimes I use Google Directions to remind me to turn when I need to.