I just renewed mine last month. Paid the expedited rate plus sent along a self-addressed pre-paid express mail return envelope, then sent the whole package outbound by express mail. Also included a little note about being a professional pilot that does frequent Int'l flights. Not sure if the last part really helped, but I got my new passport in about a week and a half. All this was recommended by the lady that handles the passport applications at my local post office.

I was being a little whiny about the fact that I had to relinquish my current passport in order to renew, yet I could be asked to cross the border at any time by my company. She took pity on me and held my hand through the whole process. She even wrote the little note. It pays to live in a small town.

Whole thing cost about $145, if I recall.