I've had really good luck with Repel Lemon Eucalyptus:

http://www.repel.com/ProductCategories/Insectrepellents/LemonEucalyptus/

FWIW, they say:

"Oil of lemon eucalyptus, in addition to DEET and Picaridin, has been recommended by the Centers for Disease Control and Prevention (CDC) for effective protection against mosquitoes that may carry the West Nile virus."

It doesn't last as long as DEET but I find it quite effective and it doesn't have all of the negatives of DEET.