Your prospects want to know more about you. Give them an easy way to check you out. It is much better to offer something interesting about yourself right up front than to have your prospects have to go searching for information about you.
I highly suggest linking out to your Linkedin profile, Twitter, or About.me page right from your email signature. And make sure your email signature is on your every response so it is very easy to find your contact information at any time.
Have you ever tried to find the contact info of someone you are supposed to have a meeting with and they don't include any in their email signature? Huge mistake.
This infographic is a nice guide to help you build out your social channels.
There are many more infographics and great stats on my Pinterest page. Enjoy!