• Income Tax Refund Status   
  
  Check the status of your federal income tax refund online.
  http://www.irs.ustreas.gov/individuals/
• Internal Revenue Code (IRC)   
  
  Search the Tax Code yourself. U.S. Code, Title 26. From the Legal Information Institute at Cornell Law School.
  http://www4.law.cornell.edu/uscode/26/
• TurboTax.com   
  
  Tax tips, newsletters, free tax tools and more. From Quicken.
  http://www.turbotax.com/
  
  • TurboTax - Tax Refund Estimator
    http://www.quicken.com/taxes/taxslashing/estimator/

• California Taxpayers' Association
  
  Protecting taxpayers from unnecessary taxes and promoting efficient, quality government services.
  http://www.caltax.org/
• Deloitte & Touche Center for Multistate Taxation
  
  http://www.uwm.edu/Dept/Business/research/salt/
• Pillsbury Winthrop Tax Page
  
  Tax bulletins, tax forms, income tax information and more. From the law firms of Pillsbury Madison & Sutro and Winthrop, Stimson, Putnam & Roberts.
  http://www.pmstax.com/
• Research Institute of America (RIA)
  
  Analysis of tax provisions, income tax news, tax alerts, information and more.
  http://www.riahome.com/default.asp
• State Government Tax Collections Data by State
  
  Provides a summary of taxes collected by state for up to 25 tax categories. These tables and data files present the details on tax collections by type of tax imposed and collected by state governments. From the U.S. Census Bureau.
  http://www.census.gov/govs/www/statetax.html
• State Tax Comparisons
  http://www.taxfoundation.org/staterankings.html
• State Tax Rates & Structure
  
  From the Federation of Tax Administrators.
  http://www.taxadmin.org/fta/rate/tax_stru.html
• Tax Cybrary
  
  Information on internet taxation, analysis of emerging tax issues, the latest sales and use tax news, and tax research. From Vertex.
  http://www.vertexinc.com/TaxCybrary/default.asp
• Tax History Project
  
  Providing scholars, policymakers, students, the media and citizens with information about the history of American taxation.
  http://www.taxhistory.org
• Taxing Electronic Commerce
  
  An exploding industry's search for clarity.
  http://www.ksre.ksu.edu/library/agec2/ep73.aspx
• Tax Topics
  
  Some of the most frequently asked tax questions and researched tax topics. From WorldWideWeb Tax.
  http://www.wwwebtax.com/master_index.htm

     See also, these cross-references:

• Income Tax Forms
  
• Legal Research
  
• Unclaimed Property Indexes