\documentclass[a4paper,12pt]{article}% voss - 2003-11-19
\makeatletter
\renewcommand\appendix{%
 \par
 \setcounter{section}{0}%
 \setcounter{subsection}{0}%
 \gdef\thesection{\@Alph\c@section}
 \gdef\@sect##1##2##3##4##5##6[##7]##8{%
  \refstepcounter{##1}%
  \protected@edef\@svsec{\@seccntformat{##1}\relax}%
  \begingroup
    \hspace{-\parindent}##6\appendixname~ {%
    \@hangfrom{\hskip ##3 \relax\@svsec}\par%
    \hspace{-\parindent}\interlinepenalty \@M ##8 \@@par}%
  \endgroup
  \csname ##1mark\endcsname{##7}%
  \addcontentsline{toc}{##1}{\protect\numberline{\csname the##1\endcsname}##7}%
  \@xsect{##5}%
 }%
}%
\makeatother

\begin{document}

\tableofcontents
\section{Some topic}
blub

\section{And another topic}
blub

\appendix
\section{Some nice appendix topic}
blubber
\section{Another nice topic}
fasel

\end{document}