From some quick internet "research" ... and because I, too, despise those little buggers:
"Because of all the deer flies this year due to a very wet spring, I thought I would repost this again. I really hate deer flies. You might look like an idiot using this method, but it really works. Deer flies appear to be attracted to the color bright Royal blue. Get a plastic Solo drinking cup that is bright Royal Blue in color. Coat the outside of the cup with something called Tanglefoot. Make sure the Tanglefoot is clear in color, not the brown kind. Walk (or drive around your property on a 4 wheeler or lawn mower)with the cup attatched to a pole or antenna, and the flies will attract themselves to the cup and get stuck. Hundreds of them will come. Why? Nobody knows. The deer flies will be completely wiped out for around two weeks. Here is a link to the study.
[link to news.ufl.edu]
PS: Due to the above observations, don't wear clothing that is Royal blue or buy a car that is Royal blue or deer flies will be attracted to you by the hundreds!"
I may start by not wearing blue shirts and see how it goes.