Legalbitstream - "Tax law research website that provides searchable databases of United States federal inome tax and estate tax law. Databases include complete and timely updated Internal Revenue Service documents and caselaw opinions from all federal courts that issue federal tax law guidance. Caselaw and IRS documents (i) contain formatting substantially similar to the original source materials, (ii) include all tables, images, appendices, and exhibits, and (iii) include formatting which permits all text, tables and graphics to print without cropping at the right page margin, which make Legalbitstream stand out among other services."
Tax History Project - Site provides scholars, policymakers, students, the media, and citizens with information about the history of American taxation. The project pursues its mission through a program of web-based documentary publication and original historical research.
Tax Statistics - Wide range of tables, articles, and data that describe and measure elements of the U.S. tax system produced by the Statistics of Income Division and other areas of the IRS.