Found this in one of those '1001 Uses For Everyday Items" books. I spray WD-40 on the inside peak and around the inner edges of my storage shed where I used to battle the buggers every year. Just a light mist, and I reapply every 3 months or so. Don't know if its the smell or if it makes it too slick for them to attach their nest, but I haven't been stung on my property in the ~5 years I've been doing it.
Works well in the mirror housing and hinge areas of the parts cars too.
DO be careful applying it to your house, tho: a buddy who tried it on his eaves ended up with a discolored blotch on vinyl siding.
I'm in SW Virginia: no idea how well this may work in other climates.
Cheers!
Scot