\usepackage {pstcol,pst-text}
\begin{pspicture}(-4,-3.2)(3,0.2)
\psset{linecolor=lightgray}
\pstextpath
{\pscurve(-4,-2)(-2,0)(0,-3)(2,-1)(3,-2)}
{\color{blue}
If you want to type
$3 \int^x_y = \sum^{n=1}_{33}$
and let it follow along a
curving line \ldots}
\end{pspicture}
