Hans, All,

\documentclass{article}
\usepackage{amsmath}

\begin{document}
I like the gather environment, useful when you don't want things
aligned on the equal sign.

\begin{gather}
f(x)=x+|x+3|-|x-3|\\
-3\le x<3
\end{gather}

I like the split environment, which allows nice formatting of
equations too long to fit on one line.

\begin{equation}
\begin{split}
f(x)&=f(x)+f'(a)(x-a)+\frac{f''(a)}{2!}(x-a)^2+\frac{f'''(a)}{3!}+\cdots\\
 &\qquad
 +\frac{f^{(n)}(a)}{n!}(x-a)^n+\frac{f^{(n+1)}(\xi)}{(n+1)!}(x-\xi)^{n+1}
\end{split}
\end{equation}
\end{document}