The Linux Symposium is a core technology conference, targeting software developers working on the Linux kernel, OS infrastructure, security, networking, and related research projects. With attendees coming from over 30 different countries, the Symposium is the single most comprehensive collection of Linux experts in the world.
2006's tutorials included "A Step by Step Introduction to Writing (or Understanding) a Linux Filesystem", "Write a real, working Linux driver" and "Reverse Engineering USB Drivers for Compatibility".
Here's their archive of proceedings which is basically a collection of very informative articles
LinuxWorld Conference and Expo
The hardware unconference where you'll learn how easy it is to make your hardware compatible with free, open source operating systems such as Linux, and available to new markets such as servers, next-generation entertainment devices, and more. Get answers on everything from kernel data structures to the fine points of licensing. Discover how participating in the Linux process is fast and simple, how the development process works, and where to get started.
FreedomHEC - from the website: "FreedomHEC is the conference where hardware vendors looking for a cost-effective Linux driver strategy can meet Linux driver experts."