I believe all of the older commemoratives are. For the moderns, all of the dollars are, but going from memory, only the Washington and Madison half dollars are silver.
The Commemorative State Quarter/Bicentennial Quarter program didn't use silver either for the regular circulation issues. Ben
Everyone (quarter) which features the individual states motto on the reverse and the bicentennial 1776-1976 quarter. They are commemoratives, not sure if the new Jefferson nickels could be considered as such though. Take Care Ben