Facebook and Twitter I always thought were for teenagers and college students. But there's one called "Linkedin" for working adults, where you could describe your skills and such. And where many pros go looking for people with your skills. http://www.linkedin.com/home?trk=hb_home
I think one problem with "social networking" sites is that there are so many of them, and there is no interoperability. It's somewhat like the old Instant Messenger services, some of which are finally getting around to offering cross-service messaging. There are workarounds for that in the form of third-party clients like GAIM/Pidgin and meebo. Not sure if any exist for the social networking stuff, although meebo has absorbed some of the messaging components.
I use Facebook; I ditched MySpace a long time ago due to spam. Facebook is headed in that direction, although it's not quite as obnoxious with the page layouts and huge ad blocks. I do have a LinkedIn account, but have only 3-4 "connections".
I have a facebook page for my business and one for my personal page, i have twitter linkin and a youtube account these were set up a couple years ago just in case. I rarely visit my linkin page most of the activity seems to be on facebook.I do like the chat feature in facebook it has come in handy when i had needed some guidance from a few contractor success groups.
I think a web page is a better way to go. It lets you control your content and from a business standpoint, you can google to a web page. I just use mine as a place to park files I want to share but the web host offers lots of business services if I wanted to use them.