What is the value of a 1995 W silver eagle?

Assuming it carries the marking 1 Troy Oz. (or similar) it's worth a bit more than the spot price of silver, currently around $12 or $13 an ounce.

That is only the value of the silver bullion. However, the 1995 W (W for West Point mint) is one of the rarest modern U.S. silver coins. It was included in the 1995 10th Anniversary Eagle Proof Set, along with the four Gold Eagle proofs for 1995. Only 30,102 1995 W were produced; over 4 million 1995 S (San Francisco mint) were produced. No uncirculated 1995 W coins were produced by the U.S. Mint.

Due to the rarity of the coin, collectors will pay thousands of dollars for a specimen. As of 15 Oct 2007, a popular internet auction site shows most listings exceeding $4,000, and some, due to the superior appearance, exceed $10,000. The value will change day to day, based on the market, but a rare coin like this will usually increase in value over time.