Showers Pass Storm Pant
Showers Pass' Storm Pants are a 2 layer fully seam-taped, completely waterproof over-pant for bike commuting. For more athletic riding you should look for a waterproof tight.
The Storm Pants feature an elastic waist with drawstring and cord lock and two specially angled hook-and-loop cinch straps on the calves to keep the pant legs from getting stuck in the chain and crank.
Includes a mesh stuff sack to make them easier to carry when you don't need to wear them.