At NECC (National Educators' Computer Convention) 2007 in Atlanta, Kathy Shrock was a featured speaker on the topic of Web 2.0 tools. Here is a link she provided to educators to help them do further research on how these tools can be used to increase student engagement and achievement.
These tools can be really fun to use. Start small. Experiment with just one, and share what you learn and how you'd like to use it.