Here are some great tax research sites for taxpayer and practitioner alike.
INTERNAL REVENUE SERVICEUnited States Federal income, gift and estate taxation.
STATE TAX AUTHORITIESLinks to all fifty U.S. states.
TAX WORLDUniversity of Illinois's Professor Omer provides this site for tax information for internet users.
ESSENTIAL LINKS TO TAXESThe definitive tax link's page
A comprehensive page of Canadian Federal tax resources. This is the
english site-they're also on the web in French.
INLAND REVENUEUnited Kingdom income taxation, including their new self-assessment tax.
TAX AND ACCOUNTING SITES DIRECTORYDennis Schmitt, associate professor at University of Northern Iowa, provides the last word on tax links pages