What is the value of a US war nickel?

So-called "war nickels" were made from mid-1942 till the end of 1945. They were struck in an alloy of 35% silver, 56% copper, and 9% manganese because nickel metal was needed for the war effort. They're distinguished by the large mint marks over the top of Monticello and by the fact that they were the first US Coins to use a P mint mark for Philadelphia.

As of 07/2010 the silver content of these coins make them worth at least $1 each. For more specific information please see the related questions linked below.

Popular misconceptions to the contrary, these are the ONLY US nickels that ever contained silver; all others are made of 75% copper and 25% nickel.