How do I clean a moldy fridge?

My roommate and I had to defrost our fridge at the end of this past semester while we would be gone for three weeks. But when it got defrosted, not all the water drained out, which we discovered when we came back yesterday. Because that fridge has been sitting there for three weeks, it has gotten a little bit moldy - not terribly so, but moldy nonetheless. What is the best way to clean this out?