xWizard
- A Tcl GUI package to generate C/C++ codes for Tcl extensions. xWizard aimed at the ease of the integration between Tcl and C. [Open source]
- http://www.neatware.com/myrmecox/studio/ex_xwizard.html

Img
- Enhances Tk by adding support for the following image formats: BMP, XBM, XPM, GIF, PNG, JPEG, TIFF and postscript.
- http://members.chello.nl/~j.nijtmans/img.html

mysqltcl - Tcl Mysql Interface
- A simple API for Mysql-Database and Tcl scripting language.
- http://www.xdobry.de/mysqltcl/

Scotty
- An extension for Tcl which provides access to network management information sources.
- https://trac.eecs.iu-bremen.de/projects/scotty/

Tcl SourceForge Project
- A portable extension that provides the power of OpenSSL to Tcl programs. This extension can be used to utilize SSL encryption on top of any valid Tcl Channel - not just sockets!
- http://tls.sourceforge.net/

TclXML
- Part of a project to make XML available to TCL programs. Two parsers are available: a front end to Expat and a native TCL one.
- http://tclxml.sourceforge.net/tclxml.html

FastBase MySQL + Tcl Interface Program
- An extension provides access to MySQL database servers using simple Tcl commands.
- http://www.fastbase.co.nz/fbsql/index.html

tcllib
- A collection of utility modules for Tcl. These modules provide a wide variety of functionality, from implementations of standard data structures to implementations of common networking protocols. [Open source, BSD License]
- http://tcl.activestate.com/software/tcllib/

[incr Widgets]
- An object-oriented mega-widget set which extends Tcl/Tk and is based on [incr Tcl] and [incr Tk].
- http://incrtcl.sourceforge.net/iwidgets/

BLT
- Add-on to the Tk toolkit, adding new widgets, geometry managers, and miscellaneous commands.
- http://incrtcl.sourceforge.net/blt/

Gnocl
- A gtk+/gnome extension for Tcl, loosely modeled after the way Tcl interfaces with Tk.
- http://www.dr-baum.net/gnocl/

[incr Tcl]
- Provides extra language support needed to build large Tcl/Tk applications by introducing the notion of objects, which act as building blocks for an application.
- http://incrtcl.sourceforge.net/itcl/

Torb
- An interface between Tcl and CORBA.
- http://www.pythontech.co.uk/torb/

TclGtk
- A project to provide Tcl with access to the Gtk GUI library.
- http://tcl-gtk.sourceforge.net/

TclSOAP
- The TclSOAP package provides a natural binding from Tcl procedures to SOAP or XML-RPC remote procedures. Both client and server support is provided.
- http://tclsoap.sourceforge.net/

NT and TCL
- Extensions designed to do Windows NT system administration through TCL scripts.
- http://qwerty.maxwell.syr.edu/nt-tcl/

Zzipp
- A package of image processing/analysis/display commands containing extensions to Tcl/Tk.
- http://users.ids.net/~eben/Zzipp/

Tix Widget Set for Tcl and Python
- Tk Interface eXtension, a set of user interface components that expand the capabilities of Tcl/Tk and Python applications.
- http://tix.sourceforge.net/

Pavia's Active Component Compound Objects
- A set of widgets extending Tk to supply object visualization.
- http://iride.unipv.it/pacco/

A HTML Widget for Tcl/Tk
- A loadable shared library widget implemented in C that interprets HTML.
- http://www.hwaci.com/sw/tkhtml/index.html

Ttclreadline
- Makes the GNU readline library available for interactive tcl shells, including history expansion and file/command completion.
- http://tclreadline.sourceforge.net/

TMath
- A Tcl Interface to MATLAB and Mathematica.
- ftp://ptolemy.eecs.berkeley.edu/pub/misc/tmath/tmath0.1/README.html

OTcl: MIT Object Tcl
- Compact extension to Tcl/Tk for object-oriented programming, from MIT.
- ftp://ftp.tns.lcs.mit.edu/pub/otcl/README.html

TCLBridge
- Allows Tcl/Tk to be used from any COM/ActiveX container, including VB, .NET, IE, and VBScript.
- http://www.tclbridge.com/

SSLtcl
- A free loadable module for Tcl that extends the socket command with SSL functions. That is, it makes it possible for Tcl applications to communicate securely over the Internet.
- http://www.abc.se/~m9339/prog/ssl/SSLtcl.html

An Introduction To Pthreads-Tcl
- Document describing the changes to Tcl that enable it to be used in conjunction with POSIX Threads (pthreads). A download for Linux is available.
- http://hwaci.com/sw/pttcl/pttcl.html

WinTclSend
- DLL to simulate keyboard input and mouse movement in Windows 95/98/NT.
- http://users.swing.be/wintclsend/index.html

Open Design and Integration Environment (ODIE)
- An extension for realtime control and simulation. It adds a realtime task switcher and a tree-structured data base, as well as a matrix expression toolkit.
- http://www.etoyoc.com/odie/

Sensus Consulting
- Featuring a binding to the LDAP C API, an extension that provides features of OpenSSL, a "pure Tcl" implementation of [Incr Tcl] and [Incr Tk], and a Tcl interpreter that allows any Tcl program to run as a Windows NT Service.
- http://www.sensus.org/tcl/

Snack Sound Extension
- Adds commands for basic sound handling and primitives for sound visualization.
- http://www.speech.kth.se/snack/