Shame they removed the tellys from 323s, are there any tellys left on trains?
Yes, in the form of Volo:TV (payable, although I believe they finally reinstated a free trial thing or at least allowed you to use the maps for free again recently) on FGW HSTs in coach D. £3.95 for a single journey (regardless of length, so best on a really long journey) or £1.50 for an hour. I've never enough credit on my phone to use the hour thing, otherwise I'm not on board for an hour or more.
Forgot, until I looked for a link, that it's on the FGW sleeper in the berths too.
http://www.volo.tv/about.html
As for this thread, I'm sure we've had one like it some months ago, but as for what I do on trains? Well most of it depends on how long my journey on board any particular train is, however a list includes:
Reading
Listening to music (did this for 8.5 hours virtually continuously last week, save for no more than 5 minutes of pausing!)
Have something to eat/drink/both
Stare out of the window if I have one nearby
Sleep
Update the notepad and/or moves book (although I do forget to do so on occasions!

)
Get bored (usually when I've nothing to do and been up and down the same line all day)
Browse a copy of the Metro/other newspaper
Use my mobile for texting/calling purposes
Time a particular section of journey (very occasionally)
Daydream
Follow the route in the atlas/Quail, colouring in new sections as I do them