Stefan Behnel - main developer and maintainer
Martijn Faassen - creator of lxml and initial main developer
Ian Bicking - creator and maintainer of lxml.html
Holger Joukl - bug reports, feedback and development on lxml.objectify
Sidnei da Silva - official MS Windows builds
Marc-Antoine Parent - XPath extension function help and patches
Kasimier Buchcik - help with specs and libxml2
Florian Wagner - help with copy.deepcopy support, bug reporting
Emil Kroymann - help with encoding support, bug reporting
Slou - help with index() support, bug reporting
Paul Everitt - bug reporting, feedback on API design
Victor Ng - Discussions on memory management strategies, vlibxml2
Robert Kern - feedback on API design
Andreas Pakulat - rpath linking support, doc improvements
Steve Howe - Windows builds
David Sankel - building statically on Windows
... and lots of other people who contributed to lxml by reporting bugs, discussing its functionality or blaming the docs for the bugs in their code. Thank you all, user feedback and discussions form a very important part of an Open Source project!