I hope no one is forgetting the benefit of having fenders and mudguards on your bikes if you do a lot of rain riding. It won't keep all the wet off, but I hear it helps a great deal.

That idea of leg gaiters is a very good suggestion! I do snowshoeing and boy do they keep my shoes and legs dry and warm!... I put them on over my rain pants and boots for the snow. These are similar to the ones i have:
http://www.rei.com/product/725915