There's no way that I want you moving a patient unless that life is in dire danger (like the car hanging on the edge of a cliff. Even then, your safety comes first, even if the car goes over with the patient in it. Don't be there too).

Shears, latex gloves (or non-), maybe some work gloves. 4x4x, some of the 5x9 abdominal pads available at drug stores, some gauze rolls, a few ace wraps. Get medical tape, not duct tape (and never apply circumfrentially). Ice packs if you want, some hot packs too (mainly for temperature control). CPR mask if you're comfortable, though that means moving a patient (see above). Maybe a few triangle bandages. Please don't splint.

Really, as a first responder, just focus on ABC's. Don't do more than that - the majority of accidents require some sort of spinal care (don't attempt) and bleeding control (do attempt)

Also, don't feel bad if the first folks on scene cut everything right off... we have to document injuries, after all!

http://forums.equipped.org/ubbthreads.php?ubb=showflat&Main=10200&Number=115963#Post115963

EDIT: Be sure if you set out flares that there isn't any fluid spillage from the accident. Last thing you want is a flashback of fire running back into a dripping fuel tank.