The last time we had those little buggers come home with my nine year old I purchased a Robi Comb from Walmart. It is a cool little contraption that zaps the lice dead but does no harm to you (similar to electronic flea combs for pets). You do have to use it daily for 2 weeks or so to make sure they are gone for good. It works on long or short hair. No nasty chemicals either or the possibility of alergic reaction if that is a problem. I have also heard that any type of heavy oil wil kill them as mentioned in the other posts. Lice really like a clean oil free scalp to live on.
Hope this helps,
L