Ruth Marcus, columnist, The Washington Post

The Center for Responsive Politics has made itself into an essential Washington — actually, make that an essential national — institution. Now more than ever, with the proliferation of super PACs and 501(c)(4) groups pouring huge sums into campaigns, it's critical to have a reliable and handy source of information on money and politics. Opensecrets.org is the go-to site for this data — trustworthy, accessible and well-presented.