I just came across an easy way to format whole columns in bold or italic style:
\usepackage{array}
\begin{tabular}{l>{\bfseries}c}
first row & second row \\
default & bold \\
\end{tabular}
There is also a possibility to format a column as math-environment. In this case, a (centered) column has to be defined as >{$}c<{$}