Ohhh I know this problem all too well !!! I travel on long trips as well (most recently over the holidays, and will be going on a 2.5 week trip in April) and it is very challenging. In fact, I thought that losing weight on a trip like this would be impossible -- but I lost 2 lbs on my holiday trip so it CAN be done. I'm nervous about the April trip but I'm also optimistic coming off my recent victory!
I wrote two blog posts about the last trip -- one before (which was very "omg this is going to be a disaster") and one after (which describes how I actually lost weight on vacation while traveling abroad and staying with food pushers!). If you're interested, they're here:
Before I left:
(not as useful) www.sparkpeople.com/mypage_public_journal_
after I got back:
(potentially useful) www.sparkpeople.com/mypage_public_journal_