Tabbing inside itemize (or itemize inside tabbing)

You could employ the tabto package for this:

\documentclass{article}
\usepackage{tabto}
\begin{document}
    \begin{itemize}
        \item It wouild be nice            \tabto{6cm} foo \tabto{7cm} bar
        \item If I could get this working  \tabto{6cm} baz \tabto{7cm} quuz 
    \end{itemize}
\end{document}

It's not entirely perfect though, as tabto does not always get the baseline right. In some occasions I had to use \raisebox or \struts to fix this.

What about a table environment or longtable for breaking across pages. Use the listliketab package

\documentclass{article}
\usepackage{listliketab}
\begin{document}

\storestyleof{itemize}
\begin{listliketab}
    \begin{tabular}{Llll}
        \textbullet &  It would be nice            & foo  &  bar   \\
        \textbullet &  If I could get this working & baz  &  quuz  \\
    \end{tabular}
\end{listliketab}
\end{document}

It has the advantage that you can use p columns to wrap long lines, etc.

Here's a (rather ugly) idea without using additional packages. Basically consists on making boxes of the desired size with \makebox:

\documentclass{article}
\begin{document}
    \begin{itemize}
        \item \makebox[5cm][l]{It would be nice}             \makebox[2cm][l]{foo} bar
        \item \makebox[5cm][l]{If I could get this working}  \makebox[2cm][l]{baz} quuz
    \end{itemize}
\end{document}