I personally find action movies quite motivating while on the bike trainer. You can only stare at the back, then front, then head cam shots of a group ride for so long!
Lack of sleep is also my nemesis when it comes to motivation. And I never seem to get enough of it :(. Alas, I have been able to hit most of my training goals so far this week. Thoughts of trying to do a 24 hr race is keeping me in line so far :)