Dan Drezner identifies a New York Times story on emailing professors. I definitely couldn't let that pass without highlighting it here.
Email is definitely the best way to approach me outside of class. It also makes a quick reply possible.
But I do get students emailing me apologising for missing class; including with excuses. That is all very nice but when I have 70 plus students, I am unlikely to notice and in any case I figure class attendence is a student's responsibility; so turn up if you want to! Of course, if you are unwell I hope you return to health too and if you have a job interview, good luck. But traffic (!), enough with the excuses already.