A very hands-on approach to modifying the sectional representation is possible by redefining \section as a whole. Vincent Zoonekynd's LaTeX website on sections does exactly this, and provides 37 different section definitions, including framing the title. Not always as pretty/clean as using a package (as in the other answers), but it does give the user control over every detail of the typesetting.

Here's example 31 in the form of an MWE, with modifications to use lipsum:

\documentclass{article}
\usepackage{lipsum}% http://ctan.org/pkg/lipsum
\makeatletter
\def\section{\@ifstar\unnumberedsection\numberedsection}
\def\numberedsection{\@ifnextchar[%]
  \numberedsectionwithtwoarguments\numberedsectionwithoneargument}
\def\unnumberedsection{\@ifnextchar[%]
  \unnumberedsectionwithtwoarguments\unnumberedsectionwithoneargument}
\def\numberedsectionwithoneargument#1{\numberedsectionwithtwoarguments[#1]{#1}}
\def\unnumberedsectionwithoneargument#1{\unnumberedsectionwithtwoarguments[#1]{#1}}
\def\numberedsectionwithtwoarguments[#1]#2{%
  \ifhmode\par\fi
  \removelastskip
  \vskip 3ex\goodbreak
  \refstepcounter{section}%
  \hbox to \hsize{%
    \fbox{%
      \hbox to 1cm{\hss\bfseries\Large\thesection.\ }%
      \vtop{%
        \advance \hsize by -1cm
        \advance \hsize by -2\fboxrule
        \advance \hsize by -2\fboxsep
        \parindent=0pt
        \leavevmode\raggedright\bfseries\Large
        #2
        }%
      }}\nobreak
  \vskip 2mm\nobreak
  \addcontentsline{toc}{section}{%
    \protect\numberline{\thesection}%
    #1}%
  \ignorespaces
  }
\def\unnumberedsectionwithtwoarguments[#1]#2{%
  \ifhmode\par\fi
  \removelastskip
  \vskip 3ex\goodbreak
%  \refstepcounter{section}%
  \hbox to \hsize{%
    \fbox{%
%      \hbox to 1cm{\hss\bfseries\Large\thesection.\ }%
      \vtop{%
%        \advance \hsize by -1cm
        \advance \hsize by -2\fboxrule
        \advance \hsize by -2\fboxsep
        \parindent=0pt
        \leavevmode\raggedright\bfseries\Large
        #2
        }%
      }}\nobreak
  \vskip 2mm\nobreak
  \addcontentsline{toc}{section}{%
%    \protect\numberline{\thesection}%
    #1}%
  \ignorespaces
  }
\makeatother
\pagestyle{empty}
\begin{document}
\section*{Introduction}
\lipsum[1]
\section{Suite}
\lipsum[2]
\section{Suite}
\lipsum[3]
\section{Fin}
\lipsum[4]
%\tableofcontents
\end{document}




Framing section headings
Is there a more colloquial term for a "confidant", or someone who has been entrusted with sensitive information to be disclosed only under certain conditions?

This is related to my previous question on trusted proxies.
