Greg is a Fellow at the Linux Foundation and is responsible for the Linux kernel stable releases. He is also the maintainer of a variety of different kernel subsystems (USB, char/misc, tty/serial, driver core, staging, etc.) and has written a few books and articles about Linux kernel development.
Wikipedia entry that is usually very out of date
Various open source code and presentations can be found at:
Books:
Articles:
How to find Greg’s email address