There is no environment appendices. There is a command appendix which introduce the appendix.
To get a list of appendix you need a new auxiliary file. In the example below the new auxiliary file gets the extension toa (t able o f a ppendix). In the next step you must declare that all entries of the appendix are written to the new file. Therefor I am using the package xpatch:
\listfiles
\documentclass[12pt,a4paper,oneside]{report}
\usepackage[titletoc]{appendix}
\usepackage{tocloft}
\usepackage{xpatch}
\makeatletter
\newcommand\listofappendixname{Table of \appendixname}
\newcommand\listofappendices{%
\if@twocolumn
\@restonecoltrue\onecolumn
\else
\@restonecolfalse
\fi
\chapter*{\listofappendixname
\@mkboth{%
\MakeUppercase\listofappendixname}{\MakeUppercase\listofappendixname}}%
\@starttoc{toa}%
\if@restonecol\twocolumn\fi
}
\g@addto@macro\appendix{%
\addcontentsline{toc}{chapter}{\appendixname}%
\xpatchcmd{\@part}{\addcontentsline{toc}}{\addcontentsline{toa}}{}{}%
\xpatchcmd{\@part}{\addcontentsline{toc}}{\addcontentsline{toa}}{}{}%
\xpatchcmd{\@chapter}{\addcontentsline{toc}}{\addcontentsline{toa}}{}{}%
\xpatchcmd{\@chapter}{\addcontentsline{toc}}{\addcontentsline{toa}}{}{}%
\xpatchcmd{\@sect}{\addcontentsline{toc}}{\addcontentsline{toa}}{}{}%
\xpatchcmd{\@sect}{\addcontentsline{toc}}{\addcontentsline{toa}}{}{}%
}
\makeatother
\begin{document}
\tableofcontents
\listofappendices
\newpage
\chapter{a1}
aaaaaaaaaaaaaaaaaa
\chapter{b1}
bbbbbbbbbbbbbbbbbbbb
\appendix
\chapter{MY}
ccccccccccccccccccccccccccc
\chapter{DFG}
dddddddddddddddd
\end{document}
\listofappendices. Do you need the packagetocloft? – Marco Daniel May 12 '13 at 09:22