If you're brand spanking new to Web 2.0, you need to pull up your sleeves and get your hands dirty. You won't be able to understand it unless you actually do it.
Concerned about protecting your computer from viruses and such? One way I minimize the risk is by checking del.icio.us. Del.icio.us is a social bookmarking site which basically means you can check to see what everyone else is bookmarking. If hundreds and thousands of people are bookmarking a site, I'm guessing that they like these websites and that downloading the software from these sites hasn't caused them any problems.
Concerned about creating an account and having sites spam you? There may actually be sites that do that, but again, I check the larger community through del.icio.us. If that many people like these sites, I'm not too concerned. And I haven't had any problems with receiving spam.
Here's a site catered to LIS professionals in schools, so it's actually designed to take you step by step into Web 2.0, introducing you to the technologies and encouraging you to interact with them. You can enroll (for free!) or work it at your own pace. Check out School Library Learning 2.0.