i have lot of experience with 10-20 hour rides, here are some things:
- gameboy (i get bored at it after 5 minutes, but obviously i am not you =.=)
- DISKMAN/MP3-PLAYER (hours and hours and hours.... i can send you some good metal & belgian techno

)
- paper (i draw alot... ofcourse on highway only)
- pocket games (you know, those classic games in smaller version for that kind of occasions)
- magic cards (if you have them.... ofcourse, other cards like pokémon are good as well, personal choice)
- enough drinks.... but no alcohol !!
- a friend/family member you like (lalz =.=)
- laptop (if you have one ofc.)
- broken things (i fixed my clock while driving to france, it kept me busy for 4 hours...)
- books (only on highway, and not in the dark, can give you headache)
- work for school (just kidding -.-)
- ...
i always enjoyed those rides with bus/car/train, i even look forward to them -.-