Credit for providing some of this information for the FAQ goes to:
Doug Neubauer (by way of James Finnegan), Jerry Jessop, Scott Emmons,
http://www.digitpress.com/

Atari 400/800 hardware engineers:
Steven T. Mayer     - early system design, overall plan
Joseph C. Decuir    - ANTIC logic design, early system design, overall plan
Jay G. Miner        - System architect (became manager of development of both
                      VLSI custom chips and OS software), overall plan
Douglas G. Neubauer - POKEY logic design (also wrote: Star Raiders)
George McLeod       - CTIA/GTIA logic design
Ronald E. Milner    - early system design
Francois Michel     - ANTIC design
Mark Shieu          - POKEY chip design
Steve Stone         - POKEY layout design
Steve Smith         - Technician for ANTIC and GTIA
Delwin Pearson      - Technician for POKEY
Kevin McKinsey      - 400/800 case design

Atari 400/800 Operating System (Revision A) software engineers:
David Crane         - OS design, programming
Larry Kaplan        - OS design, programming
                      (also wrote: Video Easel, Super Breakout)
Alan Miller         - OS design, programming (also wrote: Basketball)
Harry Stewart       - consultant, OS design
Gary Palmer         - worked on the I/O portion
Ian Shepard         - disk drive functions

Atari 400/800 Operating System Revision B fixes:
Michael P. Mahar/R. Scott Scheiman

Atari 1200XL hardware engineers:
Gregg Squires       - head of engineering.  Reported to Steve Mayer at
                      WCI Labs in New York.
Regan Cheng         - XL case design.  Reported to Roy Nishi, industrial
                      design group, Sunnyvale.

Atari 1200XL Operating System (Revisions 10, 11):
H. Stewart/Lane Winner/R. Scott Scheiman/Y. M. Chen/M. W. Colburn

Atari 600XL/800XL hardware engineers:
Gregg Squires       - head of engineering.  Reported to Steve Mayer at
                      WCI Labs in New York.
Regan Cheng         - XL case design.  Reported to Roy Nishi, industrial
                      design group, Sunnyvale.
??????????          - FGTIA

Atari 600XL/800XL Operating System (Revisions 1, 2):
(Revision 2 also commonly found in earlier XE computers)
R. S. Scheiman/Richard K. Nordin/Y. M. Chen

Atari XE systems hardware designer/engineer:
Jose A. Valdes      - at Atari from October 1979 - August 1989
Ira Velinsky        - designer of the XE game system

Atari XE Operating System (Revisions 3, 3B, 4):
??????????

Some parts © 2009 Advameg, Inc.