Some manufacturer's do offer specific PID's but they tend dependent on using exactly the same gear (Cinetank for example). I'm not aware of any central repository but happy to set one up on the Wiki if enough people are willing to contribute their information.
The Pixhawk ships with default PID's that should to a reasonable job at getting you into the air and the AutoTune feature does a fantastic job of tweaking the PID's.
Thanks for your reply, Matt :) Yes, I think it is a good idea to set up such a repository so that everyone can dump their quad set-ups together with their PIDs into it. It will certainly help newbies, like me. Is the AutoTune good enough for small 250 size quads? I was under the impression that AutoTune is still being fine-tuned for small 250 size quads, from a post (dated July 2014) I read over in the APM forum.
My quad is an ADS Spanky and it doesn't come with any recommended PIDs. Even if it does, the usual ones they support are the Naze32's and CC3D's. I guess not much people will mount a Pixhawk on a 250 quad :)