MicroEmacs is a cross platform text editor similar to Emacs but with a much smaller footprint. It does not use lisp as the scripting language but its own language. Micro does not mean "minimal functionality." In fact, MicroEmacs comes with support for many languages (Tcl included), automatic (smart) indentation, macro recording, spell checking, source browser (Tcl support included) and user extensibility via its own scripting language.
More can be learned about MicroEmacs via the home page: http://www.jasspa.com
This screen shot example is editing a simple Tcl file. You can see the buffer explorer, directory tree and file tree on the left and on the right the code browser (recognizes procs, namespaces, itcl and snit methods, typemethods, constructors, deconstructors, widgets and adapters) as well as the "abbreviation expansion" tool. There are a number of other tools you can dock, but those are what I use. You can also see that some methods are "collapsed, F2 toggles the collapsed state while Control-F2 would toggle all states. Most of the keystrokes are the same as Emacs.
MicroEmacs runs on a variety of platforms, binaries are available for anything from DOS to Windows 7, Solaris, Linux, HPUX, IRIX, AIX, Cygwin, Apple OSes, Open/FreeBSD and various PDAs.