Finding phone number by email and vise-versa?

is there a tool, site or software which if you have a persons email you can find there phone number. and likewise if you have a persons phone number can you find there email address?, need to contact a guy who i have is eamil but is not responding so i need his telephone number, just wondored if anybody knew if there was a tool that could provide such information. whether it be america, united kingdom or any where in the world?