Where can I find detailed information on IRS treatment of nonprofits?

Summary:

The IRS itself has a detailed website.

To find information about the rules and procedures for nonprofits on the IRS website, use the official term -- "exempt organizations." A great useful starting point for looking up this information on the IRS website is at http://www.irs.gov/eo

The section called "Exempt Organization FAQs" listed in the navigation panel at the left has brief answers to many frequently-asked questions about the IRS and its regulations and procedures for nonprofits.

The IRS also offers an email service that forwards updates on policies about exempt organizations and changes to the EO section of the IRS website. To learn about this service and how to subscribe, visit http://www.irs.gov/charities/page/0,,id=130596,00.html

The "Internal Revenue Manual" is online; Part 7 has detailed guidance on many questions relating to nonprofits. See this page.

Most discussions of "nonprofits" focus on "public charities" (recognized under section 501(c)(3) of the Internal Revenue Code) and "private foundations" (also recognized under 501(c)(3) but required to follow different rules in important areas of their operations). There are many other types of exempt organizations permitted under federal law; for an introduction to the full range, see the FAQ item at http://www.nonprofits.org/npofaq/16/08.html