The PBS Newshour is doing a segment Monday on "the race online" - from their media email newsletter:

The Internet is quickly becoming an important tool in political campaigning, and should have a strong role in the 2008 presidential election.  The cause for this recent phenomenon is due largely in part to the rise of popular online video-sharing websites like YouTube.com, which have simplified the transfer and sharing of information through videos on the Internet.  Sen. Hillary Rodham Clinton became the latest politician to utilize the Internet for a campaign by announcing her plans to run for president on Saturday through an online video on her website.  She also plans to participate in three live online chats starting tonight.