\documentclass[12pt]{letter}

\usepackage{graphicx}

\address{Oude Kijk in 't Jat Straat 26\\9712 EK Groningen}
\signature{\includegraphics[width=3cm]{sig2.eps}\\Bart\\Student Assistant}

\begin{document}

\begin{letter}{Bunch of students\\
               Campus Lane 22 through 29\\
               Groningen}
\opening{Dear Student:}

This is a letter style document using the {\tt letter} documentclass. 
You may rejoice now. It uses a whole load of commands to get you to 
specify chunks of information, which it typesets for you, meaning 
minimal bother for you, at least ideally. 

Well, then.
\closing{Sincerely,}
\cc{Other people who want this}
\end{letter}

\end{document}