My tweets are open to the public but probably are not that interesting to people who don't know me.
I believe Facebook is for friends so I keep my friends list to people I know.
The latest in the social media fray, Google+ is a combination of twitter and facebook
I share my personal photography on Flickr, it's great community for photographers.
The photos that I take for the Willamette University Bearcats track & cross country teams are shared on Smugmug.
Buffalo Grafix is the name I use for my website designs. It's not legally a business but it's my name.
I havn't completely bought in to the location aware social networking scene but I do occasionally check-in on Foursquare.