You can search by section, e.g. just for final rules. There is also a browse feature. Forms are available that can be filled in and printed directly from Adobe Acrobat Reader. This is the official source, but the server may be busy, especially as deadlines approach. Prior years back to 1992 are available.
Forms are retrievable by date or number, or use the search feature.
This site has IRS forms and publications in Adobe Acrobat format, and provides links to state forms. FedWorld Tax Form Search Searches theFedWorld FTP site. Nearly all states have home pages for their taxing agencies and nearly all of these offer downloadable forms. Tax and Accounting Sites Directory by Dennis Schmidt, Associate Professor of Accounting, University of Northern Iowa. Very well organized and easy to navigate.