IRS Homepage http://www.irs.ustreas.gov/
IRS homepage has information on tax statistics, general information, information for businesses and individual taxpayers, electronic filing services, news, forms and publications.
Federation of Tax Administration http://www.taxadmin.org/fta/FORMS.html Contains the list of downloadable tax forms for each state.
IRS Forms and Publications http://www.irs.ustreas.gov/prod/forms_pubs/ Contains current year forms and publications which can be downloaded, as well as information regarding forms and publications.
The Tax Prophet http://www.taxprophet.com/ A site for those who want to keep up to date on the latest information in tax law; provides analysis of Internal Revenue Code.