Curved Text

\usepackage{pstricks, pstcol, pst-text}

\begin{pspicture}(-4, -3.2)(3, 0.2)
  \psset{linecolor=white}     % hidden
  \pstextpath
    {\pscurve(-4, -2)(-2, 0)(0, -3)(2, -1)%
      (3, -2)(5, -3)}
    {\color{blue}             % font color
      If you want to type
      $(a+b)^n=\sum_{k=0}^n {n\choose k}
       a^{n-k}b^k$ and let it follow along 
       a curving line \ldots}  
\end{pspicture}