Sites we like:

R.O.W.E. - Results-Only Work Environment. In a ROWE, people are paid for a chunk of work, not for a chunk of time. This simple idea creates a workforce that is energized, focused, disciplined, and happy. 

AFP - Association of Fundraising Professionals, standard-bearer for professionalism in fundraising.

Charities Review Coucil - An independent resource for people who make contributions to support charities, dedicated to empowering givers in making informed and thoughtful giving decisions, so they can be more effective in helping charities advance  important community work.

GuideStar - Gathers and publicizes information about nonprofit organizations and encourages nonprofits to share information about their organizations openly and completely. A great resource for everything from 990's to mission information.

Council on Foundations - A national nonprofit association of more than 2,000 grantmaking foundations and corporations that strives to increase the effectiveness, stewardship, and accountability of the philanthropic sector.