Regexp and Regsub
Online chapter from Tcl/Tk for Programmers (with exercises and solutions).

Helpful TCL/TK notes
Miller, based on the John Ousterhout tutorial. By Michael S.

Overview of Tk
This chapter introduces Tk, an extension of Tcl that supports GUI, or graphical user interface, programming. Online chapter from Tcl/Tk for Programmers (with exercises and solutions).

Browser Plugin and Safe-Tcl
Online chapter from Tcl/Tk for Programmers (with exercises and solutions).

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.

How do I learn Tcl?
lang. A series of tips posted to comp.

Geometry Management
This chapter covers two of the three geometry managers Tk has, grid & place. Online chapter from Tcl/Tk for Programmers (with exercises and solutions).

E.J. Friedman-Hill's Tcl/Tk Course
Tcl/Tk Programming in Five Easy Lessons.

Basic Syntax and I/O
This chapter covers much of Tcl's basic syntax as it applies to command lines. An online chapter from Tcl/Tk for Programmers (with exercises and solutions).

Perl and the Tk Extension: Using X from Perl
An article on the Tk toolkit from the Perl Journal.

An Introduction to Tcl and Tk
Tcl with its X Window toolkit adds command scripts and user interfaces to both standalone tools and applications.

Variety of tutorial resources
Including how to create new Tcl/Tk commands, how to add Tcl to a C application, and how to use C++ objects in Tcl.

Introduction to Tcl/Tk
By Alex Samonte: 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.

Will's Guide To Success with Tcl 8.0 Namespaces and Packages
A guide to using namespaces and packages.

TclTutor
It consists of 43 lessons covering all of the basic Tcl commands and most of the recent (8. A computer aided instruction package for learning the Tcl language.