Is a 1999 mint condition silver dollar coin worth anything?

It depends what kind of coin you have.

If you have a small (26.5 mm) coin with a really unattractive picture of Susan B. Anthony on the front, it's copper-nickel rather than silver and is only worth $1.

If you have a large (40 mm) coin with Miss Liberty walking in a flowing gown and the Words 1 oz FIne Silver or similar on the back, it's a bullion piece sold for its silver content and not for spending; the $1 denomination is artificial. In that case its value will change along with the price of silver. As of 12/2009 that's about $17.