Pros: This site basically acts as an outlet for you to connect online to your instant messaging accounts. The sight is a host to AOL Instant Messaging (AIM), Yahoo, MSN, and Google Talk. I've found that it is a great way to keep in touch with people instantly when you are on a computer that does not have the instant messaging program you use.
Cons: The only downfall is that some of the screen names are saved differently than at-home IM programs. For example, at home I put in everyone's first and last name on display, and now I don't know their SN. It is a problem on meebo because it usually only displays the person's sn.
Pros: This site is mostly for meeting people instead of reconnecting with people you already know. You can friend, or "favorite" a person, and then instantly chat with them via webcam.
Cons: The webcam sessions expire at 2 minutes. Clearly not enough time to get to know anyone. Also, I found it is more of an online dating site than anything else.
Pros: This networking site allows people to look for a job, look to fill a company's position, or to simply interact with former colleagues and classmates. On this site, you can post your resume, past experiences, skills, training, etc. Also, someone can write a recommendation for you to give you an extra boost in the job market.
Cons: Not enough people know about it yet! While I am still finding people to join my network, I am discovering that most of the people I know (professionals or students) haven't heard about linkedin.