As you already know, I have started two weeks ago tagging (and asking others to tag) their CPS sites on del.icio.us with the tag "cps-site". I think we have spotted about 80 public CPS sites so far, but I'm sure many are still missing.
BTW: how do you know a website is a CPS site? There are several clues: 1. Look at the icon, if present. 2. Look at the urls (if it contains "section" it's probably a CPS site). 3. Look at the HTTP "Server" header.
Now I have a similar idea: there are many Trac site out there, and Trac is one of the "Python killer-apps". So let's tag also Trac sites with the trac-site tag and see what happens.