tree list in a table

You can use dirtree within a table, just enclose the mark-up within a minipage and be careful with the stops at the end of the lines! Here is a minimal example:

\documentclass{article} 
\usepackage{dirtree}
\begin{document}
\begin{tabular}{|l|l|}
\begin{minipage}{4cm}\dirtree{%
.1 Engineering.
.2 Mechanical.
.3 Electrical.
.4 Electronics.
}\end{minipage}    
& \begin{minipage}{4cm}\dirtree{%
.1 TeX.
.2 LaTeX.
.3 XeTeX.
.4 pdfLaTeX.
}\end{minipage}\\
\end{tabular}
\end{document}

Edit as per comments

\begin{tabular}{|l|p{3cm}|}
\begin{minipage}[t]{4cm}\dirtree{%
.1 Engineering.
.2 Mechanical.
.3 Electrical.
.4 Electronics.
}\end{minipage}    
&  Director A  
   \newline Director B 
   \newline Director C
   \newline Director D\\
\end{tabular}

This will produce an output as requested (two columns) the third is trivial! For anything more fancy I would use a graphics package such as TikZ or pstricks. This sort of layout IMHo is better produced using, just minipages and or specially constructed environments. Nevertheless dirtree is a great package and one can use it for all sorts of different problems.

Here is a direct solution (based entirely off of Yiannis's answer) which solves the problem.

\documentclass{article} 
\usepackage{dirtree,array}
\setlength{\extrarowheight}{3pt}
\begin{document}
\begin{tabular}{|l|l|l|}
\hline
\multicolumn{1}{|c} {Heading 1} & \multicolumn{1}{|c|} {Heading 2} & \multicolumn{1}{c|}{Heading 3}\\
\hline
\begin{minipage}{4cm}\dirtree{%
.1 Engineering.
.2 Mechanical.
.3 Bio-mechanical.
.2 Electronics.
}\end{minipage}
&
\DTsetlength{0pt}{0pt}{0pt}{0pt}{0pt}
\begin{minipage}{6cm}\dirtree{%
.1 Stuff about engineering here.
.2 Stuff about Mechanical here.
.3 Stuff about biomechanical here.
.4 .
}\end{minipage}
&
\DTsetlength{0pt}{0pt}{0pt}{0pt}{0pt}
\begin{minipage}{4cm}\dirtree{%
.1 Comments.
.2 More comments.
.3 Still more.
.4 And more.
}\end{minipage}\\
\hline
\end{tabular}
\end{document}
&
\DTsetlength{0pt}{0pt}{0pt}{0pt}{0pt}
\begin{minipage}{6cm}\dirtree{%
.1 Stuff about engineering here.
.2 Stuff about Mechanical here.
.3 Stuff about Electrical here.
.4 .
}\end{minipage}
\end{tabular}
\end{document}

Here an example how you can mimic that with pure table environment. But you don't have connections between sub-items.

Hope that helps anyway.

\begin{table}[p]
\begin{center}
    \caption{Some caption of your table} \label{tab:trendtable}
    \begin{tabular}{lll}
    \midrule[1pt]
    \multicolumn{1}{c} {Heading 1} & \multicolumn{1}{c}{Heading 2} & \multicolumn{1}{c} {Heading 3} \\ 
    \midrule[1pt]
    \textbf{main-item}             & main item data        & some info\\
    \hspace{0.2cm} sub item 1      & sub item 1 data       & some info 1 \\
    \hspace{0.4cm} sub sub item x  & sub item 1.x          & some info x \\
    &&\\
    \textbf{main-item 2}           & ...                   & ...\\
    \hspace{0.2cm} ...             & ...                   & ... \\
    \end{tabular}
\end{center}
\end{table}