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 Carl Friedrich Bolz Maciek Fijalkowski Michael Hudson Antonio Cuni Christian Tismer Holger Krekel Eric van Riet Paap Richard Emslie Anders Chrigstrom Aurelien Campeas Amaury Forgeot d Arc Anders Lehmann Niklaus Haldimann Seo Sanghyeon Leonardo Santagada Lawrence Oluyede Jakub Gustak Guido Wesdorp Niko Matsakis Toon Verwaest Alexander Schremmer Ludovic Aubry Alex Martelli Stephan Diehl Adrien Di Mascio Stefan Schwarzer Tomek Meka Patrick Maupin Jacob Hallen Laura Creighton Camillo Bruni Bob Ippolito Simon Burton Bruno Gola Alexandre Fayolle Marius Gedminas Guido van Rossum Valentino Volonghi Adrian Kuhn Anders Hammarquist Paul deGrandis Gerald Klix Wanja Saatkamp Oscar Nierstrasz Eugene Oden Lukas Renggli Bartosz SKOWRON Guenter Jantzen Dinu Gherman Georg Brandl Ben Young Nicolas Chauvat Jean-Paul Calderone Rocco Moretti Michael Twomey Boris Feigin Jared Grubb Olivier Dormond Stuart Williams Jens-Uwe Mager Justas Sadzevicius Brian Dorsey Jonathan David Riehl Beatrice During Elmo Mäntynen Andreas Friedge Anders Qvist Alan McIntyre Bert Freudenberg Pieter Zieschang Ignas Mikalajunas Jacob Oscarson Lutz Paelike Benjamin Peterson Michael Schneider Artur Lisiecki Lene Wagner Christopher Armstrong Joshua Gilbert Jacek Generowicz Gasper Zejn Stephan Busemann Yusei Tahara Godefroid Chappelle Toby Watson Andrew Thompson Gintautas Miliauskas Anders Sigfridsson Neil Shepperd Michael Chermside tav Igor Trindade Oliveira Martin Blais Victor Stinner