An awesome start up allowing you to do exactly this and more is http://flowtown.com. Their main feature is allowing you to convert email address into social profiles, you can really learn a lot about a person by what they post online - a great way to learn your customer base online.
Businesses that care about their customers / users / clients are the ones that will win in 2010 and beyond. I want to be apart of this future and it's the basis for why @danmartell and I founded Flowtown.
I can vouch for Ethan and say he has personally emailed me a few times to let me know how things are going (with regards to some of my suggestions) and I can tell you he generally cares.
I mean, I don't know him outside of a few email transactions but in any case, he either truly cares or is really good at faking his authenticity, I will go with the former. This would be the reason I recommended his service and the reason I am trying to utilize it at my current place of employment. (head office is not very quick on approvals)
