If you do not want to give your actual phone number to the people you talk to and GrandCentral is not solving the purpose for you then try out this latest service, Jangl.
Jangl is a weird and a potentially very useful service that assigns a unique phone number to every relationship. That means instead of giving out your phone number to everyone you can just tell him your Jangl ID and if that person wants to call you he can just visit the official Jangl we-site type in your ID and get a unique relationship number.
When you call on that number you will leave an invitation message and that if accepted by the concerned person, makes you both connected.
The good thing about this service is that anyone of the two parties involved can end the relationship and that expires the relationship phone number. Since no one knows the actual phone number you again have to repeat the whole procedure if you have to call the person.
The procedure though a bit long will surely help safeguard your personal number and Jangl is also launching a SMS code, which will ease your pressure.