Vinegar!!! Also, plantain weed, which is very common, but vinegar is usually the easiest to get a hold of. I keep it in a reclaimed bottle from lens cleaner for my glasses and keep it in our first aid kit (which is mainly vinegar, baking soda, & sodium ascorbate powder). Spray it wherever I need it. It's also great for sunburn.
I've gotten vastly fewer bites the last two summers. We went camping this weekend and I got just 3 or 4 - I used to get 20-30 on each leg on a weekend like that, using strong bugspray (just used gentle California Baby and only used it twice). I'm certain it has to do with diet - I don't know if it's a stronger immune system that keeps me from reacting as strongly (are they not biting, or am I not reacting?) or, another theory I read recently, whether my more stable blood sugar is keeping them away. The theory was that low blood sugar attracts them, observing that diabetics apparently don't get bitten?