• Answers.com on Nonprofits - scroll down to the Small Business Encyclopedia section of the page for well-written overview on nonprofit organizations.
• Anthony Mancuso, How to Form a Nonprofit Corporation, Nolo Press, 8th ed., 2007 - a great resource to have when forming a nonprofit corporation.
• Bruce R. Hopkins, Starting and Managing a Nonprofit Organization, John Wiley & Sons, Inc., Fourth ed., 2005 - another terrific book to use when considering the nonprofit route.
• The Nonprofit Road - an article in the Columbia Journalism Review which has information about nonprofit journalism ventures.
• The Bottom Line for Nonprofit News - an article by Ryan Blitstein on the financial aspect of running a nonprofit newsite.
• The Non-profit Good Practice Guide - a guide that provides valuable resource directories and general tips for all aspects of nonprofit management.
• Is a Not for Profit the way to go? - a terrific resource from Illinois Legal Aid which is aimed at helping the reader consider whether to embark on a nonprofit venture.
• 8 Mistakes to Avoid in Starting a Nonprofit Corporation and New Nonprofit Startup Checklist - two helpful resources by T.S. Wrobel and Associates.
• ChiTown Daily News: Misunderstanding Nonprofit News

Formation
Important IRS Publications on forming a nonprofit:

• Publication 557: Tax Exempt Status For Your Organization
• Form 1023
• IRS requirements for exemption under 501(c)(3)
• Application Process for Non-Profits
• IRS Guide to applying for exemption

Operation

• A Basic Guide to Non-Profit Financial Management - published by the Free Management Library, this guide covers skills such as cash management and bookkeeping.

Tax Treatment

• Unrelated Business Tax Income (UBIT) - the IRS guide on the special rules covering UBIT.

Fiscal Sponsorship

• Fiscal sponsorship: the state of a growing service - a report commissioned by The Trust For Conservation Innovation that examines details of the business model including types of sponsored activities, fees, and revenue levels. The report also contains a good list of local and national sponsors to consider.
• Fiscal Sponsorship - an article by Greg Colvin on how to decide whether a fiscal sponsorship is appropriate.
• FAQ on Fiscal Sponsorships - written by the Foundation Center, an organization that is dedicated to strengthening the nonprofit sector.
• New York Foundation for the Arts - the largest provider of grants, services, and information to artists working in all disciplines in the United States.
  
• The San Francisco Foundation - a nonprofit organization that provides fiscal sponsorship to community efforts in identified circumstances, including philanthropic collaborations among foundations, community efforts responding to crises, and projects of limited duration.