Everyone's marriage will come into a slump at some point of time, it's only natural. I bet even Pam Anderson and Tommy Lee had a few slumps every now and then. If this happens take the bull by the horns and get yourself one of these things that will really bring you back up to some good passion.
It works becuase it's different, a little naughty bringing you back to a simpler time before you were married and while you were courting. Enjoying the adult pleasures together is so much better then you standard ho-hum sex life. Another thing you can try is having sex OUTSIDE of the bedroom like the kitchen counter or living room.