If you use LinkedIn, go change your password now.
A good article on it can be found here
The stolen passwords have been posted on the Internet for a couple of days now, so assume your password has been compromised. This is particularly true if your password is a word in a dictionary, or a name. Good passwords should be at a minimum 8 characters long (more is better), and contain at least one of each of the following: Upper and lower case letters, numbers, and symbols.
If you use the same password for LinkedIn that you use for other accounts, go change them as well. Yes, all of them. Once a cracker has a known username/password combination they will try it on other sites as well.
Got questions? Ask. Please. It's better to know than it is it get taken.