TeamWave developed a variety of collaboration tools, using 
Tcl and Tk extensively.

The standalone product, TeamWave Workplace, featured a Tk-based
desktop application offering whiteboard, chat, and a variety of
other collaborative tools.

The later web based versions didn't require users to download 
client software.
Though Tk was not used for the GUI (it was Java-applet based, again
so that no download is required), Tcl and a Tk-like API were used
on the server to drive the user interface.

The various products were written in a mix of Tcl and C, and relied
on MetaKit for storage.  The web versions also used AOLserver.

For more information, contact [Mark Roseman].

The company was acquired in late 2000.
The original web site [http://www.teamwave.com] has since been 
shut down, but Mark maintains a retrospective site
[http://www.markroseman.com/teamwave/] with some additional links
and information.