Does anybody know of a good compilation, regarding mechanical properties of thermoplastics or in general polymers?
I suggest MatWeb:
MatWeb's searchable database of material properties includes data sheets of thermoplastic and thermoset polymers such as ABS, nylon, polycarbonate, polyester, polyethylene and polypropylene; metals such as aluminum, cobalt, copper, lead, magnesium, nickel, steel, superalloys, titanium and zinc alloys; ceramics; plus semiconductors, fibers, and other engineering materials.
There are 84,173 entries in the Polymers tab in the physical properties search page at the time of my writing this. Note that you can select up to 3 properties at a time to narrow your search (or 10 if you pay for the service: MatWeb is a freemium deal, so be sure to look into whether or not your needs are satisfied by the free/pay versions.)