In any business or social setting, business cards are the most cost effective way to make an impression. It’s interesting that people seem to see business cards as such an institutionalized medium for passing out traditional contact information that they overlook the impact of adding social media contact information.
I started putting my social networking info on the back of my cards about a year ago, and my goal is to refine the design enough that I can present either side: Strict business or social.

I try to keep it uncluttered with just website, blog Linkedin, Facebook and Twitter info, plus my mobile for the texters.
For my next edition: better formatting.
Tip: I hate that cumbersome URL for my facebook profile, so I bought http://spakebook.com and point that at my FB profile URL.