Ralph Smith's Formal Font [http://www.ctan.org/tex-archive/fonts/rsfs/] provides a bit more cursive caligarphic symbols. They can be used inside ConTeX by
<texcodecontext source="yes">
\def\mathrsfs#1{\text{\definedfont[RalfSmithFormalScript]#1\/}}
\mathrsfs{ABCDEFGHIJKLMNOPQRSTUVWXYZ} </texcodecontext>
'''Note:''' Since this is an italic script, one needs italic correction <code>\/</code> in the definition.