Centering a table wider than the text column

I’d recommend trying the chngpage package.

\documentclass{article}

% allows for temporary adjustment of side margins
\usepackage{chngpage}

% provides filler text
\usepackage{lipsum}

% just makes the table prettier (see \toprule, \bottomrule, etc. commands below)
\usepackage{booktabs}

\begin{document}

\lipsum[1]% just a paragraph of filler text

\medskip% adds some space before the table
\begin{adjustwidth}{-1in}{-1in}% adjust the L and R margins by 1 inch
  \begin{tabular}{ll}
    \toprule
    Sequence & Wide column \\
    \midrule
    First & Vestibulum porta ultricies felis. In nec mi. \\
    Second & Nam vestibulum auctor nibh. In eleifend, 
    lacus id tristique ullamcorper, mauris urna convallis elit. \\
    Third & Ut luctus nisi quam lobortis magna. Aenean sit amet odio 
   et sapien rutrum lobortis. \\ 
    Fourth & Integer dictum accumsan purus. Nullam erat ligula,
    dictum sed, feugiat nec, faucibus id, ipsum. \\
    \bottomrule
  \end{tabular}
\end{adjustwidth}
\medskip% adds some space after the table

\noindent\lipsum[2]% just a paragraph of filler text

\end{document}

The documentation for the chngpage package is located at the bottom of the chngpage.sty file. I’ve pulled out the docs for the adjustwidth environment:

Within an adjustwidth environment
the left and right margins can be
adjusted. The environment takes one
optional argument and two required
length arguments:

\begin{adjustwidth}[]{leftmargin}{rightmargin}

A positive length value will increase the relevant margin

(shortening the text lines) while a
negative length value will decrease
the margin (lengthening text lines).
An empty length argument means no
change to the margin. At the end of
the environment the margins revert to
their original values.

For example, to extend the text
into the right margin:

\begin{adjustwidth}{}{-8em}

Any appearance of the optional
argument (even just []) will cause the
values of the margins to switch
between odd and even pages.

If the document is being set
twosided it might be advantageous to
have any wider text extending into the
outside margin. This could be done via
the optional argument, as:

\begin{adjustwidth}[]{}{-8em}

To have the adjusted text
horizontally centered with respect to
any surrounding text, the margins
should be adjusted equally:

\begin{adjustwidth}{-4em}{-4em}