The Treasury Inspector General For Tax Administration (TIGTA) hosts a site we like: www.treasury.gov/tigta/ 
This website is a major portal designed for anyone interested in tax initiatives, tax administration, basic research and information regarding new tax impacts. The site has separate sub-portals for citizens, preparers and tax professionals. An individual may sign up and subscribe for all new data and informational releases for a multitude of different tax areas. This is all free of charge.
The portals for “Congressional Testimony” and “Semi-Annual Reports” contain a wealth of historical information, easy to read and understand, analyzing tax administrations and new initiatives. The site also provides information regarding how the IRS operates and tax audit data. The right-hand side of the portal provides access to topics that the IRS is focusing on for compliance and audit purposes.
This is a very user-friendly web-site providing access to all current and historical tax topics.