Tcl/Tk

Most Tcl resources can be found through <http://dev.scriptics.com/>,
and the sources and related projects accessed through 
<http://sourceforge.net/foundry/tcl-foundry/>.

You can download standalone versions of Tcl and Tk for MacOS from there.
Tcl (and Tk) on MacOS are now largely supported by Jim Ingham in his spare
time, with some help from others.  If you'd like to help with, for instance,
Carbonizing Tk, or building in support for MacOS specific features (e.g.
proxy icons, drag and drop, etc), the source code is freely available.  The
newsgroup <news:comp.lang.tcl> is both active, and full of very helpful
people (including all the most active developers of Tcl and many Alpha
developers) so it's often a good place to look for more information, and to
coordinate work in specific areas.

Another useful resource is the Tcler's Wiki <http://purl.org/thecliff/tcl/wiki/>

There are also a number of good books on Tcl/Tk, both for beginners
and for experts.

Please note that Alpha 7.x has an embedded Tcl 7.5 interpreter
(approximately -- there are some differences).  Alpha 8 will use either 
Tcl 8.3 or 8.4, and Alphatk makes use of whatever Tcl/Tk interpreter
you have installed (at least 8.1 or newer).