The IRS website includes forms, pubications, schedules and much more.
ABA Section on Taxation - Includes section news, ABA positions on tax policy issues, meeting dates and selected articles from Tax Lawyer.
Internal Revenue Service Official website of the IRS. Includes forms, publications, as well as tax information for individuals, businesses, and non-profit organizations.
Tax History Project - a public service initiative from Tax Analysts. Established in 1995, the Project provides scholars, policymakers, journalists, and the general public with information on the history of U.S. public finance. Interesting information includes Presidential tax returns, historical tax forms from 1913-2006, and tax related cartoons and posters.