There is a dimension defined for doing just that: \itemindent.
\begin{itemize}
\addtolength{\itemindent}{5cm}
\item The first item
\item The second item
\end{itemize}
Note that \itemindent is reset at the start of the itemize environment, so you need to adjust it after \begin{itemize}. If you'd like the same indentation on all your lists, you could define a new environment which defines this:
\newenvironment{indentitemize}{%
\begin{itemize}%
\addtolength{\itemindent}{5cm}%
}
{%
\end{itemize}%
}
and use it just like a normal itemize environment. (This I havent tested, but I assume it works...)
A complete example:
\documentclass{article}
\begin{document}
This is some text before the list.
\begin{itemize}
\addtolength{\itemindent}{5cm}
\item The first item
\item The second item
\end{itemize}
\end{document}
Output:
