Beamer: Removing headline and its space on a single frame (for plan), but keeping the footline

Ok, after more investigation (in the beamer sources :)), I have found the solution. For those who will search like me in the future, here it is in a simple small example :

{ % to delimit a block (we only want to remove the header for this frame)
\makeatletter % to change template
    \setbeamertemplate{headline}[default] % not mandatory, but I though it was better to set it blank
    \def\beamer@entrycode{\vspace*{-\headheight}} % here is the part we are interested in :)
\makeatother
\begin{frame}{Table of contents} % and our simple frame
    \tableofcontents
\end{frame}
}

It is also possible to define an environment to be able to use it more easily. To do so, use this part of code before the \begin{document} :

\makeatletter
    \newenvironment{withoutheadline}{
        \setbeamertemplate{headline}[default]
        \def\beamer@entrycode{\vspace*{-\headheight}}
    }{}
\makeatother

And for your frame :

\begin{withoutheadline}
    \begin{frame}{Table of contents} % and our simple frame
        \tableofcontents
    \end{frame}
\end{withoutheadline}

Hope this will help :)

Enjoy!

\makeatletter
\newenvironment{noheadline}{
    \setbeamertemplate{headline}{}
    \addtobeamertemplate{frametitle}{\vspace*{-0.9\baselineskip}}{}
}{}
\makeatother

With this little modification you can use noheadline environment for several slides together.

\begin{noheadline}
\begin{frame}{Table of contents} % and our simple frame
    \tableofcontents
\end{frame}

\begin{frame}{Table of contents 2} % and our simple frame
    \tableofcontents
\end{frame}
\end{noheadline}