What is the value of a 2009 silver US quarter?

If the quarter has an "S" next to the tail of Washington's wig and does not have the normal copper edge of a quarter found in pocket change, it's almost certainly a so-called "Prestige" quarter that someone accidentally spent.

These coins were only sold to collectors and weren't intended for spending It was worth about $8 in its original packaging but if you got it in change as of 02/2011 it's worth about $5 to $6 for its metal content.

If your coin has a P or D next to Washington's wig, or has an S but shows a copper edge, it's not silver. It's made of copper-nickel like almost all other quarters minted since 1965. With a P or D it has no added value. An S indicates it was a proof coin that someone spent. That which reduces its original $1.15 collector value to, well, roughly a quarter.