I have Butler Creek "Blizzard" scope covers on two rifles. They're clear so you can see without flipping them up. They're invaluable when it's snowing! I only put them on the front of the scope because, when I'm carrying the rifle, the eye piece is down and doesn't get wet.
Got them through MidwayUSA.com for about $5 each; about $8 everywhere else I looked.
me!