I find that that the only acceptable repellent is one that contains DEET (N,N-diethyl-m-toluamide) in relatively heavy concentrations. Two that come to mind are Muskol and Ben's. Yes, I know that apparently the body does absorb some of the dope and that the effects of it on humans (if any) are not known. Still, if you really need protection, I feel that it is the way to go. If you can find a product with 35% or more DEET in it you're in business. I find that Off and even Deep Woods Off are not that great (low DEET concentrations). If the bugs are present but not terrible I just go without and put up with the occasional bite. This stuff works well for for mosquitos, noseeums, deer flies and especially black flies.
For more info about DEET, go to the url below. Keep in mind that this info is put out by the industry that makes the stuff.
<a href="http://www.reillyind.com/deet/content/htm/deetnews.htm" target="_blank"><!--auto-->http://www.reillyind.com/deet/content/htm/deetnews.htm</a><!--auto-->
Hope this helps.