I did some shooting at an airshow in the rain just a few weeks ago. Overall, I'm not really happy with my shots. I struggle with the flat light and backlit effect of the low overcast.
I managed to get this one accepted, but I'm not crazy about it:
View Large View Medium
Photo © Jason McDowell
I kind of like this one, but I'm still debating whether or not to upload it:
I definitely second the recommendation to use a hood. With a good hood and the wind at your back, you can shoot without getting drops on your lens.