I have not seen one on the web yet. There are the ones that come with the CD (examples installed under the /proe2001/toolkit/protk_appls folder). There are a few sites with freeware/shareware apps including this one - but unless you plan to decompile them, then sourcce code is not available.
The only way I learned it was to go through the API (under Proe2001/Toolkit/protkdoc folder) . Thankfully, I had a condensed version of the course given to me too so that helped alot, and if you can get your hands on a copy of the PTC training guide then that would also be beneficial.
On the other hand, I just realized that maybe you are already a Toolkiter and just want some extra resources. If that is the case, then I am afraid that I have found little out there. If you do come across anything decent though, I would appreciate it if you could send me the link (rbrunetATadscaDOTcom)