Great.  Mojca suggested that I wikify my Emacs lisp.  It's now at
<http://wiki.contextgarden.net/Text_editor>.  Following that method ('a
method is a trick I use twice.' --Polya), I've put your elisp there too
-- hope that's okay.  I removed the

            (local-set-key "$" 'start-context-math)

so that your code can stand alone (in case people want one or the
other).

I had to change a few things at the end (some maybe because I'm using
GNU Emacs rather than XEmacs, not sure).  Below is the diff and I've
attached the resulting version.  Most of the trouble was in the
keybindings:

	    (local-set-key "\C-c\C-fc" 'context-insert-FLOW-cells)

doesn't work because C-c C-f is already defined as TeX-font, so it can't
be a prefix as well.  So I chose "\C-cnF".  Also the function name
needed an "s" at the end.  These two:

	    (local-set-key "\C-cnn" 'context-insert-nattab)
	    (local-set-key "\C-cnr" 'context-insert-nattab-row)

have a related problem, in that "\C-cn" is not a prefix yet, so "\C-cnn"
and "\C-cnr" are not valid sequences.  So I changed the first use of
"\C-cn" as a prefix to use define-key(), which seems to make a
prefix-map automatically as I eventually learnt by inspecting tex.el.
So:

	    (define-key (current-local-map) "\C-cnF" 'context-insert-FLOW-cells)
Then the following local-set-key's work.  As I say, this is on Emacs
21.4, and the tricks may be different on XEmacs.

-Sanjoy

--- a/tables.el	2006-04-20 10:46:16.000000000 -0400
+++ b/tables.el	2006-04-20 10:43:41.000000000 -0400
@@ -1,5 +1,5 @@
 (defun context-insert-nattab (rows columns)
-  ;; Johan Sandblom 060128
+  ;; Johan Sandblom 2006-01-28
   "Insert a TABLE skeleton"
   (interactive "nNumber of rows: \nnNumber of columns: \n")
   (newline)
@@ -44,8 +44,8 @@
  (newline)
  (backward-char 5))
 
-(defun context-insert-FLOW-cell (n)
- ;; Johan Sandblom 060128
+(defun context-insert-FLOW-cells (n)
+ ;; Johan Sandblom 2006-01-28
  "Insert a FLOWchart cell"
  (interactive "nNumber of cells: \n")
  (newline)
@@ -62,8 +62,7 @@
 
 (add-hook 'ConTeXt-mode-hook
          '(lambda ()
-	    (local-set-key "\C-c\C-fc" 'context-insert-FLOW-cells)
+	    (define-key (current-local-map) "\C-cnF" 'context-insert-FLOW-cells)
 	    (local-set-key "\C-cnr" 'context-insert-nattab-row)
 	    (local-set-key "\C-cnc" 'context-insert-nattab-column)
-	    (local-set-key "\C-cnn" 'context-insert-nattab)
-            (local-set-key "$" 'start-context-math)))
+	    (local-set-key "\C-cnn" 'context-insert-nattab)))