Debian includes a package called "vrms - virtual Richard M. Stallman" which report the non-free packages you have installed on your Debian system. Running vrms on my workstations gives the following output:

makholm@makholm:~$ vrms   
              Non-free packages installed on makholm

gcc-4.2-doc               documentation for the GNU compilers (gcc, gobjc, g++)
gcc-doc-base              several GNU manual pages
sun-java6-bin             Sun Java(TM) Runtime Environment (JRE) 6 (architecture
sun-java6-jre             Sun Java(TM) Runtime Environment (JRE) 6 (architecture
sun-java6-plugin          The Java(TM) Plug-in, Java SE 6
xsnow                     Brings Christmas to your desktop

  6 non-free packages, 0.4% of 1487 installed packages.
makholm@makholm:~$

Sun Java is a know evil and somebody really ought to reimplement xsnow, but having the virtual RMS declare GNU documentation non-free is a nice touch. Yeah, I know about the problems with GFDL.

Update: Known problem: #221807, #297506, and #364971