Most likely what you're after is to insert a rubber length that stretches with your content. In LaTeX, this is provided by \hfill. You can insert it between two pieces of text, or any construct that sets in horizontal mode (like a tabular):

\documentclass{article}
\begin{document}
\noindent
Some content on the left \hfill% <----- rubber length
Some content on the right
\bigskip
\noindent
\begin{tabular}{@{} p{.4\linewidth} @{}}
\raggedright
Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Aenean orci odio, sollicitudin sed lectus et, accumsan porttitor erat.
Donec imperdiet rutrum nibh quis sodales. Nunc sagittis orci enim,
a egestas enim congue et.
\end{tabular}\hfill% <----- rubber length
\begin{tabular}{@{} p{.4\linewidth} @{}}
\raggedleft
Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Aenean orci odio, sollicitudin sed lectus et, accumsan porttitor erat.
Donec imperdiet rutrum nibh quis sodales. Nunc sagittis orci enim,
a egestas enim congue et.
\end{tabular}
\end{document}
If you want a rubber rule, use \hrulefill. If you want a rubber dot fill, use \dotfill. Alternatively, use a construction of some leader.