Here's a nice slide show about how the Internet is effecting the political activities of American citizens.  The information is based on new research by the Pew Internet and American Life Project. It's more about information-gathering and deliberation than organizing and activism, but I guess you gotta start somewhere.

Here are the key findings:

• Citizen 2.0 voters represent 51% of American voters
  
  • Citizen 2.0 voters are no different demographically
    
  • they considerably different in terms of skepticism towards traditional media and are more engaged with searching and sharing political information with friends and family
  • They search for information online when