Consider the following:
\documentclass{article}
\setlength\parindent{0pt}
\begin{document}
content \hfill content
\begin{tabular*}{\textwidth}{l@{\extracolsep{\fill}}r}
one & two \\
three & four
\end{tabular*}
content \hfill content
\end{document}
How can I remove the whitespace at either side of the tabular?
While \setlength{\tabcolsep}{0pt} will do the job in your example, it's better in general to insert @{} in front of the first column and after the final column to eliminate the whitespace (in the amount of \tabcolsep) that LaTeX inserts by default in these locations.
For the case of your example, you'd write
\begin{tabular*}{\textwidth}{@{} l @{\extracolsep{\fill}} r @{}}
instead of
\setlength{\tabcolsep}{0pt}
\begin{tabular*}{\textwidth}{l @{\extracolsep{\fill}} r}
The approach based on inserting @{} particles is better because it works not only with tabular* but also with tabular, tabularx, tabulary, and so on.
\setlength{\tabcolsep}{0pt}solves this issue. ('Doh!) – Sean Allred Jan 08 '14 at 06:07@{}in front of the first column and after the final column to eliminate the extra whitespace. I.e., one would write something like\begin{tabular*}{\textwidth}{@{}l@{\extracolsep{\fill}}r@{}}. One reason this it better is because it works with all other tabular-type environments, viz.,tabular,tabularx,tabulary, etc. – Mico Jan 08 '14 at 06:28