OpenIsis provides a library and tools to access CDS/ISIS databases, which are mostly used for bibliographic data (ISO2709, Z39.50) but also well suited for other catalogues due to the very flexible indexing mechanism. Based on a C library, there are also bindings for Perl and Java (Tcl to come).
xmmstcl lets you control XMMS playback, skip, pause, change the playlist, change skins, and do everything else provided by the xmms_remote_* methods, which is almost everything from the standard user interface. It also has some things not available there, such as "XMMS onchange" which lets your Tcl/Tk application know when something happens in the player. The companion "TkPlayer" has samples for the most important functions and will keep XMMS busy by generating random playlists with songs that you haven't heard in a while.
tkxinput contains Xi, a library that adds Xinput management capabilities to the Tk toolkit, and a utility named calibrate that can be used to test various aspects of the Xinput configuration of an X server. calibrate can be used, as its name implies, as a touchscreen calibration facility.
IRK is a Tcl IRC client library. IRK is intended for Tcl programmers that want to use the IRC protocol for communication. It can be used to ease the creation of IRC "bots", to serve as the basis for graphical chat clients, and to allow IRKs to find each other without centralized coordination by meeting on a designated IRC server and channel. This last feature makes it ideal for negotiating the initial contact of P2P programs without requiring a central registry or server.
Extended Tcl (TclX) is an extension to Tcl, the Tool Command Language invented by Dr. John Ousterhout. Tcl is a simple and powerful embeddable programming language. Extended Tcl is oriented toward system programming tasks and large application development. TclX provides additional interfaces to the operating system. It also adds many new programming constructs, text manipulation tools, and debugging tools.
The GOBLIN project consists of a C++ class library for a large series of graph optimization problems, GOSH, an extension of the Tcl/Tk scripting language to graph objects, and GOBLET, a graphical user interface to the library functions. GOBLET includes a graph editor and supports the standard graph layout methods.