People really don't give Tcl enough credit. Some do, but most really don't. The day really belongs to Java, which has attracted a lot of the newer developers lately. However, I think that as a first language for implementing small to medium sized apps, Tcl is ideal. Better yet are applications which embed Tcl as an extension language. This brings me to my point.
Lately, I've been using the XiRCON IRC client as my primary IRC application. I like apps like Chatzilla, but there seems to be a lack of automation, probably due to the fact that Chatzilla is embedded within a XUL application. It might be possible to do JavaScript (ECMAScript?) extensions in Chatzilla, but there doesn't seem to be a good IRC API availab le within Chatzilla for script developers (I'd be happy to be proved wrong on this).
XiRCON embeds Tcl as an extension language. Syntactically, Tcl is extremely easy to learn, as it has very few concepts to deal with. This in contrast to applications which extend with languages like Perl, which requires some attention in order to do things right, or a custom scripting language (except lua -- I heart lua too, but not as much as Tcl). As such, fitting a mental model of an application into your brain when it's expressed in Tcl is far easier. There are fewer language specific issues to deal with -- you really get to focus on the application API, rather than attempting to get the language syntax right.
I think that Tcl within XiRCON is a shining example. You can mix arbitrary Tcl commands and procedures with IRC commands (preceeded with a / character), and hook Tcl procedures to a wide variety of events coming from your IRC server. Right now, I'm using this functionality to join a standard list of channels, and notify the nickserv that I've arrived. Arguably a simple usage of such a powerful set of features. However, it would be easy to write Bots directly in XiRCON, which puts this client on par with XChat, which is arguably the best GUI IRC client available today.
I would have loved to use XChat on Windows XP, but I just cannot justify paying for XChat when I can get similar functionality for free from XiRCON! Sure, XChat has a larger base of scripts, as well as a number of plugins for other extension languages (Perl and Python, as well as Tcl). However, with Tcl XiRCON provides the right language for extending an IRC client.
