The linegoal package provides a macro \linegoal to be used with
\setlength: \setlength<some dimen>\linegoal will set <some
dimen> to the horizontal length of the remainder of the line.
This is achieved using the \pdfsavepos primitive of pdftex,
through the zref-savepos package. Example: Some text:
\begin{tabularx}\linegoal{|l|X|} \hline one & two \\ three &
four \\\hline \end{tabularx} will position the table after the
initial text, and make the table fill the rest of the line.
