The tables below, list some of Google's eclectic mix of open source luminaries grouped by project.
No doubt I've forgotten some, so don't hesitate to contact me with corrections/additions.
Note also this list of Google's open source projects.

Python
Alex Martelli Python Cookbook, ...
Brett Cannon Python
Jeremy Hylton Zope
Neal Norwitz PyChecker
Collin Winter functional, unladen swallow
Mark Pilgrim Books, libs
Anthony Baxter release manager, libs
Jim Hugunin numeric, jython, ironpython
Linux Kernel
Andrew Morton  
Daniel Phillips  
Ted T'so  
Ross Biro  
Paul Menage  
Richard Gooch  
Tom Herbert Networking
Eric Dumazet Networking
Subversion (Google Code)
Ben Collins-Sussman  
Brian W. Fitzpatrick  
Daniel Berlin  
Greg Stein  
Peter Lundblad  
Eric Gillespie  
Mozilla / Chromium
Ben Goodger  
Darin Fisher  
Brian Ryner  
Fritz Schneider  
Mike Pinkerton  
Aaron Boodman GreaseMonkey
Eric Seidel WebKit
Peter Beverloo WebKit
John Barton Firebug
Community relations
Chris DiBona from Slashdot
Andy Hertzfeld from Apple, Eazel
Jason Robbins tigris.org
Tim Bray from Sun
Zaheda Bhorat from Openoffice
Zach Brown Kernel Traffic
Misc
Rob Pike UNIX, UTF8
Ken Thompson UNIX, UTF8
Russ Cox Plan9, RE2
Eric Grosse Plan9, Netlib
Peter Weinberger aWk
Stuart Feldman Make
Van Jacobson TCP/IP, tcpdump, ...
Vint Cerf TCP/IP
Udi Manber Glimpse
Raph Levien Gimp, Ghostscript, ...
Peter Mattis Gimp
Spencer Kimball Gimp, Gnutella
Josh MacDonald PRCS, xdelta, GTK+
Junio Hamano git
Sean Egan Pidgin
Jon Trowbridge Gnome/beagle
Behdad Esfahbod Gnome, HarfBuzz, ...
Scott James Remnant dpkg, upstart, ...
Ronald S. Bultje ffmpeg
Craig Silverstein distcc, ...
Dan Kegel Wine, crosstool, ...
Ian Lance Taylor GNU toolchain
Roland McGrath GNU Make, glibc, ...
Stefano Lattarini GNU AutoMake, ...
Diego Novillo GCC optimization
Daniel Ehrenberg Factor
Glen Murphy Browser stuff
Joe Gregorio Atom, python libs
Han-Wen Nienhuys Lilypond
Bruno Albuquerque openBFS
T. V. Raman Emacspeak
Murray Stokely FreeBSD core team
Nik Clayton FreeBSD docs, ...
Amit Singh OS X system stuff
Frank Mayhar UNIX kernel stuff
Ben Laurie openssl, apache-ssl
Neil Fraser diff-match-patch, ...
Bernie Innocenti OLPC
Tim Hockin linux system utils
Avery Pennarun bup, redo, ...
Adam Langley ObsTCP
Michal Zalewski security tools
Tavis Ormandy security tools
Chris Evans vsftpd, security ...
James Youngman findutils, ...
Brad Fitzpatrick web server tools
Robert Love Gnome/kernel/books
David Reveman compiz, XGL
Jean-loup Gailly zlib
Bram Moolenaar Vim
Martin Pool distcc, launchpad, ...
Jeremy Allison Samba
Eric Schmidt (CEO) Lex

Gradually Google is becoming less secretive, especially so since 2005/2006. Consequently it can attract high profile people from the open source community, on whose technologies it depends so much. As well as employing those above and many others involved in open source, it has begun to interact more with the community. For example Google has started to release internal tools, provide an open source project hosting service and runs the very cool Summer of Code initiative. These are definitely not trivial undertakings. For instance Google has spent the following on the Summer of Code project:

Project Students Amount
SoC 2005 400 $2.0M
SoC 2006 600 $3.0M
SoC 2007 900 $4.5M
SoC 2008 1125 $5.6M
SoC 2009 1000 $5.0M
SoC 2010 1025 $5.6M
SoC 2011 1116 $6.1M

This is money well spent as they get better open source software, kudos from the community and also get an early view of blossoming open source stars. I notice Fedora as of 2010 has started the "Fedora Summer Coding" program. Other notable Google hackers not directly involved in open source are:

Name Previous experience
Peter Norvig NASA
Andrew Moore Carnegie Mellon
Steve Lawrence CiteSeer
Mike Burrows altavista, Microsoft (spam research)
David Hanson Microsoft: compiler research
Martin Taylor Microsoft: linux strategist, VP of live
Joe Beda Microsoft: Avalon, IE
© Apr 27 2010