A couple of businesses have asked me to help them get set up with Facebook, Linked In, Twitter, and so on. I don’t have any idea what would be a fair price and what services and prices to offer / charge to update them. I would appreciate some practical suggestions. Thanks!

If your doing this work for pay then you are considered a business. You must have a business license and you must pay all federal, state, county and city taxes, associated these.
Don’t forget to get liability insurance to protect your self should you get sued!
This income must be reported on your annual tax statement.
$18.00 – $25.00 dollars and hour is common charged made by professionals.