Here is a list of developers who have committed to the PyPy source code base, ordered by number of commits (which is certainly not a very appropriate measure but it's something):
Armin Rigo Samuele Pedroni Michael Hudson Carl Friedrich Bolz Christian Tismer Holger Krekel Eric van Riet Paap Antonio Cuni Anders Chrigstrom Maciek Fijalkowski Richard Emslie Aurelien Campeas Anders Lehmann Niklaus Haldimann Seo Sanghyeon Lawrence Oluyede Alex Martelli Ludovic Aubry Adrien Di Mascio Stephan Diehl Guido Wesdorp Stefan Schwarzer Tomek Meka Patrick Maupin Leonardo Santagada Bob Ippolito Laura Creighton Jacob Hallen Marius Gedminas Niko Matsakis Amaury Forgeot d Arc Guido van Rossum Valentino Volonghi Alexander Schremmer Alexandre Fayolle Wanja Saatkamp Gerald Klix Eugene Oden Dinu Gherman Guenter Jantzen Ben Young Nicolas Chauvat Michael Twomey Rocco Moretti Simon Burton Boris Feigin Olivier Dormond Gintautas Miliauskas Stuart Williams Jens-Uwe Mager Brian Dorsey Jonathan David Riehl Anders Qvist Beatrice During Andreas Friedge Alan McIntyre Bert Freudenberg Pieter Zieschang Jean-Paul Calderone Jacob Oscarson Ignas Mikalajunas Lutz Paelike Christopher Armstrong Yusei Tahara Andrew Thompson Jacek Generowicz Joshua Gilbert Anna Ravencroft Martin Blais Michael Chermside