Your opinion: web sites promoting volunteering gigs (USA)?

Whether you have lots of experience using different web sites to search for volunteering gigs/tasks/opportunities, or would be looking at these web sites for the first time per this question, here's a question:

What is your opinion of the following web sites promoting volunteering opportunities for multiple organizations, mostly in the USA? What do you like about them, what do you not? Which do you use/would you use regularly?

VolunteerMatch (http://www.volunteermatch.org)/

IdeaList (http://www.idealist.org)/

Change.org (http://www.change.org)/

Network for Good (http://www.networkforgood.org/)

http://www.1-800-volunteer.org/

ServeNet (http://servenet.org/)

Your local edition of CraigsList (http://www.craigslist.com)/

Other sites listing volunteering opportunities for multiple organizations in the USA?