The best advice I have for people who want to use web 2.0 (social networking tools and communities) to promote their cause is to make it easy for your supporters to be your advocates.  Make them celebrities for your cause.

Seth Godin calls this "Flipping the Funnel." Let your supporters hold your megaphone for you and your message will be amplified many times.  They are celebrities among their families and friends, and they can be great spokespeople for you! After all, the number one reason people give money or take action is because someone asked them-especially someone they know.  So how do you give your core supporters ways to be evangelists for your cause? 

1. Send them a nifty email and ask them to forward it to five friends.  Make it an email that just asks for a simple action, like signing a petition or joining a community so you can get the email addresses of those five friends and cultivate them as donors. 

2. If they have a blog, ask them to link to you or fundraise for you on their blog.  Give them cool tools to do it - such as the charity badge found at sixdegrees.org.

3.  Send your supporters cool pictures or put them on Flickr and ask people to share the good work you are doing.  Pictures are extremely compelling and help you establish an emotional connection.

4. Ask your supporters to hold events for you, like dinner party fundraisers or races and make it easy for them to recruit people with tools like First Giving.

5. Ask them to tell their stories to you and then share those stories on your website or in emails. The personal stories your supporters have about why they support you are often far more interesting and compelling then any appeal you could create. 

6. Go to Technorati.com, a search of blogs, and type in things relevant to your cause.  Check out all the bloggers talking about your issue and develop a relationship with them.  Ask them for ideas and see if they will tell their readers about your work.  Why create a blog when there are bloggers out there talking about your ideas already?  They are celebrities in their spheres, however small.