Piatnitzkysaurus is a little bare on the internet. In general the sites that do discuss Piatnitzkysaurus are well done sites that address the facts, present them, and are pretty aesthetically pleasing. I picked out a top three and, in no particular order, here they are.
NHM of London: Presented as a very short list of facts, the illustration that is used is very outdated, but the concise nature of it is great.
About: Performing as we expect, the description and listed facts of About are wonderful, as usual for teaching the most important facts to dinosaur enthusiasts that do not know Piatnitzkysaurus.
Cool Dino Facts: An even more concise list of facts. Use this site as a support site in discussing the dinosaur at best.