Currently there are only some packages for debian lenny hosted here. These packages are partialy modified for the use with applications by geops and are not intended for general use.
Add the following line to your /etc/apt/sources.list :
deb http://www.geops.de/apt lenny mainor
deb http://www.geops.de/apt squeeze main
... to stop apt complaining over unverified signatures
sudo apt-key adv --keyserver hkp://keys.gnupg.net --recv-keys B6AA9BC9E7BDBF3D