How to suppress subsections in the table of contents in latex-beamer?

The same as in the other two answers can also be achieved using \setcounter{tocdepth}{1}, before (or after) \begin{document}: try to compile the following code, then delete or comment the line marked with %%% and compile again (once, or twice if necessary) to see the difference.

\documentclass{beamer}
\usetheme{Goettingen}

\setcounter{tocdepth}{1} %%%

\begin{document}

\frame{\tableofcontents}

\section{First}
\begin{frame}
  A
\end{frame}

\section{Second}
\subsection{One only}
\begin{frame}
  B
\end{frame}

\end{document}

At the same way as using \tableofcontents[hideallsubsections], the subsections disappear in the frame where the \tableofcontents is, but not in the sidebar (if present in the theme you use). The same, again, with local use of starred \subsection*{Subsection Title}.

To hide subsections use the pretty self-explanatory:

\tableofcontents[hideallsubsections]

To keep a specific subsection out of the index use: \subsection*{...}

To remove all subsections from the TOC only, use: \tableofcontents[hideallsubsections] (added from another answer)