BiggerPockets is the premier social network for real estate professionals, investors, and consumers, with a focus on shared knowledge, networking, deal making, and marketing.
http://www.biggerpockets.com
The Flipping Pad is a website created to help people share and discuss real estate investing. Discuss, find, compare and enjoy flipping homes from around the world. A social network for real estate investors.
http://www.flippingpad.com
MyAgentBook.com is an online social network community for real estate agent professionals, providing the opportunity for members to communicate with each other across the country for the purposes of building and cultivating professional relationships, sending or receiving referrals and sharing professional information.
http://www.myagentbook.com