The latest release of Notepad++, a Windows OS based open source text editor, supports Tcl syntax highlighting. It can be downloaded at the following web address: 

http://sourceforge.net/projects/notepad-plus


[JMN] 2005-11-29  This seems like a fairly nice usable editor.. but the Tcl syntax highlighting is not quite there yet.

Some issues I've noticed:

problem 1) If a tcl comment line contains 'if' as the first 
element - notepad++ incorrectly starts a new nesting 
level - putting other sections out of sync.

e.g the following line is mishandled.

 # if blah blah blah

problem 2) Escaped brackets aren't matched properly.

e.g the following sorts of lines are mishandled (incorrect bracket-match highlighting)

 set x {abc\{d}
 set y [list a b\[c d]
 set z [list a {b[c} d]