NHSkier's post stating Bizer.com has the gas tax refund form is correct but their form is outdated (theirs is dated 1/2007 while the current form is dated 10/2008). And as Green's Basin Girl mentioned, her link isn't working (Page Not Found).
Here's the link to the Road Toll Refund Application for OHRV's, snowmobiles and boats,
http://www.nh.gov/safety/divisions/a...ents/RT123.pdf. I too buy the majority of my fuel on the road (I trailer my boat) and just write my name and bow number on each receipt when I send them in. Make sure you send in the ORIGINAL receipts; they don't want copies (make photocopies for your records).