Web Design & Usability

No, not Facebook.  What I mean is integrating social usability into a website by allowing user chat, opinions, and reviews...among other things.  The voices of your customers, employees, and critics can be an invaluable tool.
Features / Options To Include

• User-to-User Chat
• Question / Answer
• Discussion Forums
• Customer Reviews
• Support Forums
• Polls/Survey

What Can They Do For Me?
You are probably not going to want to incorporate all of these...probable nightmare for your users.  All of them have their benefits,-which vary depending on your overall design and strategy.  User-to-user chat is great for support, specific questions or questions with complex answers, they are also a great just way for users to interact with each other and not just an admin of sorts.  Everyone knows what poll and surveys are good for...allow the users to give some input on some person, place, thing, or idea.  Wikis are a cool way that allow users to build content, however monitoring this can be a huge task.  The are tons of different uses and benefits but there are a few things to keep in mind:

• Make Sure There Is A "Business" Reason
• Plan For It In Your Original Web Design
• Define What Results You Want/Need And What You Plan To Do With Them

In summary, social feature can be extremely useful in determining how your users feel, just make sure you plan for it.  A stack of data without a plan is a pile of junk, if you have a plan for that data it becomes information.