Here is how to install Microsoft core TrueType fonts in Debian which is useful if you need to work with documents created on a Windows system.
Step 1: Edit /etc/apt/sources.list to include "contrib" as a source
...
deb http://ftp.uk.debian.org/debian/ squeeze main contrib
deb-src http://ftp.uk.debian.org/debian/ squeeze main contrib
...
Step 2: Update apt and install the fonts
sudo apt-get update
sudo apt-get install ttf-mscorefonts-installer