Make ToC in the center and left aligned in beamer

Question

Using the following code I could put the ToC lines in the center in beamer:

\begin{frame}
  \begin{center}
  \tableofcontents
  \end{center}
\end{frame}

But how to make these ToC lines left aligned and still in the center?

Answer 1

A small calculation could advance the margins sufficiently to obtain the centered & left-aligned \tableofcontents display.

\documentclass{beamer}% http://ctan.org/pkg/beamer
\newsavebox{\longestsec}% Box to save longest sectional heading
\begin{document}

\begin{frame}
  \frametitle{Table of contents}
  \begin{lrbox}{\longestsec}Last section in the presentation\end{lrbox}% Capture longest title
  \setlength{\leftskip}{\dimexpr.5\textwidth-.5\wd\longestsec\relax}% Advance left margin accordingly
  \tableofcontents
\end{frame}

\section{First section}
​\begin{frame}
  \frametitle{First slide}
  This is a slide.
\end{frame}

\section{Last section in the presentation}% Longest sectional title
\begin{frame}
  \frametitle{Another slide}
  This is another slide
\end{frame}
\end{document}

​The reason for this round-about way is because beamer collapses the spacing when putting \tableofcontents within a minipage or varwidth (from the varwidth package).