LinkedIn (www.linkedin.com) - Another good website to use in conjunction with ActiveRain
If you don't already know about it, LinkedIn.com is a great professional networking site for various business professionals.
It doesn't have quite the blogging capability, a personal feel or resulting Google Juice that ActiveRain has, but it's a great way to connect with other professionals.
I remember earlier this year I had an issue with a short sale, and I was able to find some Executive VP's at the bank where my shortsale was held.
It was because of that connection that I was able to get the short sale expedited.
If any of you have some history with LinkedIn, let me know what you think of it.