I've just remembered something that helps me get some work done. I sometimes try to write a short document or long email on the laptop on the way to work.
The advantage of doing it on the train is that there is a limited amount of time before I reach my station, so I have to try and produce a complete plan/piece of work in that small time window. There are days when I get a lot more done on the train than in the office!
One important factor must be that there is no internet connection on the train! That helps a lot! I sometimes think I should just work from the train the whole time, occasionally stopping off at the office to sync my files!