Someone just posted a comment lamenting the fact that HM's often check out a candidate via social networks, etc. Why not be upfront and indicate any social networks, eg, LinkedIn, Facebook, etc. Why not provide a thumbnail photo as well, at least for sales or public-interface positions. I am not being too self-promoting I hope in mentioning that I have just put up a website called eBusinessCard.net which if ideal for just this purpose. It's free so I stand to gain nothing if recruiters use it, but it's something to take a look at as a possible recruiting tool.
Your candidate can include an optional photo and list all his contact and social networking URL's in the context of a discrete business card which can be inserted in resumes, emails, etc.