I had a sizeable checking account built up prior to the trip. I had all bills that could be auto-debited done that way. If not, I either prepayed and/or prepared a SASE with a prepayment given to a relative who has given a list of when to mail what letter. This way I never had to rely on a public computer to do bill paying, something I personally would avoid if possible.
As far as taxes go, I filed in October as I knew I would be getting a small refund. YOu must have a "good" reason as to why you could not file but it is almost always allowed. However, you must pay any taxes due prior to April 15th or you might be subject to penalty and interest. However, if you are gone a year, your tax situation might be pretty easy and you could have someone file on your behalf.
I would give a trusted family memeber/friend a limited power of attorney so they could discuss stuff with the bank, credit card company, etc. if need be.
Finally, you might want to ask those over at CGoaB who have done extended tours what they have done also.
Happy trails and may the wind be at your back!