One often requires that the abstract of a paper should appear across the entire page, even in a two-column paper. The required trick is:
  \documentclass[twocolumn]{article}
  ...
  \begin{document}
  ... % \author, etc
  \twocolumn[
    \begin{@twocolumnfalse}
      \maketitle
      \begin{abstract}
        ...
      \end{abstract}
    \end{@twocolumnfalse}
  ]
Unfortunately, with the above \thanks won't work in the
\author list.  If you need such specially-numbered footnotes, you
can make them like this:
  \title{Demonstration}
  \author{Me, You\thanks{}}
  \twocolumn[
    ... as above ...
  ]
  {
    \renewcommand{\thefootnote}%
      {\fnsymbol{footnote}}
    \footnotetext[1]{Thanks for nothing}
  }
and so on.
As an alternative, among other facilities the abstract package 
provides a
\saythanks command and a onecolabstract environment
which remove the need to fiddle with the \thanks and
footnoting. They can be used like this:
\twocolumn[
  \maketitle             % full width title
  \begin{onecolabstract} % full width abstract
  ... text 
  \end{onecolabstract}
]
\saythanks               % typeset any \thanks
This question on the Web: http://www.tex.ac.uk/cgi-bin/texfaq2html?label=onecolabs