C-5,
I've never personally done this but I do know of a few people who have had good luck with renewing their passports at a consulate or embassy... quick and easy, you can do it with a couple of days layover on a trip. However, I don't think you can just "walk into" a consulate, embassy, or passport agency and renew anymore, you have to have an appointment. I've renewed a few times by mail and it's also painless... you can get the form off the Dept of State website (just make sure you get the form for renewals and not initial application). If you need it really quick you can pay an extra fee and have it expedited. FWIW, I've found that it's quickest to send it to the Charleston office (and I don't live anywhere near CHS). I don't know why but it seems to be so. Just my experiences... hope it helps.
cc