An Introduction to Tcl and Tk
Tcl with its X Window toolkit adds command scripts and user interfaces to both standalone tools and applications
E.J. Friedman-Hill's Tcl/Tk Course
Tcl/Tk Programming in Five Easy Lessons
How do I learn Tcl?
a series of tips posted to comp.lang.tcl for learning more about Tcl
Introduction to Tcl/Tk
After completing this tutorial, you will be able to understand what Tcl and Tk are, understand the basics of Tcl and Tk and create simple Tcl/Tk applications
Perl and the Tk Extension: Using X from Perl
an article on the Tk toolkit from the Perl Journal
Tcl/TK quick start
Tcl/TK quick start introduces the Tcl/Tk scripting language, including its history, key features of the language and interpreter, some extensions, and several examples of Tcl/Tk in action.
a computer aided instruction package for learning the Tcl language. It consists of 43 lessons covering all of the basic Tcl commands and most of the recent (8.0) additions
Will's Guide To Success with Tcl 8.0 Namespaces and Packages
a guide to using namespaces and packages