Online versions of the man pages for Tcl and Tk can be found at:
This wiki also has documentation for a lot of the Tcl and Tk commands. The fundamental charter of Tcl is the "Endekalogue". The Wiki Endekalogue page lists translations (of the Tcl reference page) to more languages. Check the manpages page for a list of more.
Among the ways to access "the manual pages" are
Translated manual pages
When writing documentation, a developer has to decide in what form to provide the documentation. There are various tools available to assist in this.
There is a tool called txt2man (see http://freshmeat.net/projects/txt2man/ ) which is said to convert plain ASCII text into man page format.
There are Tcl specific tools, such as dtp/doctools software, which provides the ability to write doc in a general form, then to generate various file formats for display purposes. TMML and dtp are two tools designed to help Tcl developers document Tcl extensions and applications. Others can found at the Source Documentation Tools page.