Tracking the popularity of a package over time?
http://popcon2.net/
Popcon² is a website for viewing and analyzing Ubuntu's user-submitted package statistics.
Update: The site is down since 2014. There is a copy on archive.org.
I've found this for Debian at http://qa.debian.org/popcon.php
For example cmatrix packages: https://qa.debian.org/popcon.php?package=cmatrix
Edit: Here's a bug with a solution.
There is also www.lesbonscomptes.com/upopcon/ and ubuntu-popcon.43-1.org/
The first one has more display options and data for a longer period (disclosure: its mine...)