i think pretty much everyhing has been covered above.
other things you might need for your CAR/TRUCK/TRAILER!!!!!!!.......
spare trailer tires,
car/truck tire removal tools,
a JACK.......
i say this because my 2nd trackday this year, i had a trialer tire blow out just before the track, adn didnt have a spare

and i would have been screwed without a jack...... which i dont usually have on me (car audio is more important

)