A LaTeX Beamer presentation (slide deck) with a long table of contents as generated by

\tableofcontents

may run off screen.

Fix

add to LaTeX preamble (near top of main .tex file):

\usepackage{multicol}

Then the TOC slide will go over multiple columns. In this example Beamer slide, two column table of contents is specified:

\frame{
\begin{multicols}{2}
\tableofcontents
\end{multicols}
}