Twitter has been really working well for my business and is just plain ole' fun. It really has the shortest learning curve of any of the social networking options out here.
The best thing I did was add Twitterrific to my desktop - which basically allows you to write and receive tweets without having to use your browser. Twitterrific is specifically for Mac users, but I'm sure there are tons of PC options out there.
As soon as you write an article, post to your blog, or watch a cool TV show - you can post it to twitter and all your friends will instantly see what you're up to.
You can follow me at: http://twitter.com/girlshrink