gorets (which means 'greedy pigs' in French) is a small Debian utility to find out which packages are eating disk space on a given partition. For instance, if /usr/share is a separate partition:
gorets /usr/share will tell you whose fault it is, if /usr/share is full. It is an unofficial package but it works for me. Bug reports (to the author) are welcome (with the output of gorets -v, please). You can get it from: ftp://ftp.internatif.org/pub/debian/UNOFFICIAL/ or you can add this in apt's sources.list: deb ftp://ftp.internatif.org/pub/debian/UNOFFICIAL ./ and then 'apt-get update' and 'apt-get install gorets'.