What is the value of a 2000 silver US quarter?

You have to inspect your coin carefully. If it has a P or D mint mark, it's made of copper-nickel, not silver and is only worth 25¢.

If it has an S mint mark and a copper-colored edge it's a copper-nickel proof coin worth maybe $2 to $10 depending on its quality.

If it's in a holder labelled "Prestige Proof", then it IS a 90% silver coin. These were made for collectors and sell for $3 to $12 depending on quality and which state is depicted.