Hello,

from the wiki (http://wiki.contextgarden.net/Math/basic#List_of_All_Math_macros) I tryed the following snippet:
\usemodule[fnt-25]
\showmathfontcharacters

But context complains that there is no fnt-25 module, so let’s grep showmathfontcharacters in conteXt directory.
I found that it is defined into the mat-10 module. So new snippet:
\usemodule[mat-10]
\showmathfontcharacters

End new error:

ConTeXt  ver: 2012.09.11 20:36 MKIV  fmt: 2012.9.12  int: english/english

system          > cont-new.mkiv loaded
(/opt/context-minimals/texmf-context/tex/context/base/cont-new.mkiv
system          > beware: some patches loaded from cont-new.mkiv
)
fonts           > latin modern fonts are not preloaded
languages       > language en is active
(mathsymbols.tex
resolvers       > modules > loaded: 'mat-10'
(/opt/context-minimals/texmf-context/tex/context/base/s-mat-10.mkiv))
fonts           > defining > font with asked name 'unknown' is not found using lookup 'file'
fonts           > defining > unknown font unknown, loading aborted
fonts           > defining > unable to define unknown as [thedefinedfont--0]
! LuaTeX error <main ctx instance>:22: attempt to index local 'resources' (a nil value)
stack traceback:
        <main ctx instance>:22: in function 'showmathfont'
        <main ctx instance>:1: in main chunk.

system          > tex > error on line 5 in file /opt/context-minimals/texmf-context/tex/context/base/cont-yes.mkiv: LuaTeX error  ...

 1     %D \module
 2     %D   [       file=cont-yes,
 3     %D        version=2012.06.01,
 4     %D          title=\CONTEXT\ Miscellaneous Macros,
 5 >>  %D       subtitle=Startup Stub,
 6     %D         author=Hans Hagen,
 7     %D           date=\currentdate,
 8     %D      copyright={PRAGMA ADE \& \CONTEXT\ Development Team}]
 9     %C
10     %C This module is part of the \CONTEXT\ macro||package and is
11     %C therefore copyrighted by \PRAGMA. See mreadme.pdf for
12     %C details.
13     
14     % At some point I will reconsider the \starttext .. \stoptext
15     % wraping as we can assume proper styling. It's a left-over from

<argument> ...cument.showmathfont(font.current())}
                                                  
\firstoftwoarguments #1#2->#1
                             
\doshowmathfontcharacters ...wmathfontcharacters }
                                                  \endgroup 
<to be read again> 
                   \finishjob 
l.5 \finishjob
              
}   context.finishjob()
                                                  
...
l.86 \stopluacode


I do not realy care about this list, I was just currious and it did not work so I point it out.