SoonerTax.com
Geared towards Oklahoma residents. Includes Federal and Oklahoma tax information as it relates to individuals, investors, students and small businesses.
Armchair Millionaire
Find most of the IRS forms and links to dozens of IRS publications in Acrobat files.
Federal Tax Return
Includes information about the 16th Amendment, as well as a glossary ofterms and useful links.
Will Yancey's Home Page
His site is great for small business owners, offering help not just with numerous tax links but also with things like credit references and links to state laws.