Here is a selection of blog posts written by GNOME Shell developers and designers about it.
GNOME Shell 2.28.0 – A Preview - 2009-10-07 by Owen Taylor
Application-Based Desktop - 2009-09-01 by Colin Walters
Getting the Message - 2009-07-05 by Jon McCann
Overview Changes - 2009-07-05 by Marina Zhurakhinskaya
GNOME Shell Status - 2009-02-09 by Owen Taylor
GNOME Shell Status - 2008-11-23 by Owen Taylor