The books and references that others have listed are certainly helpful. In fact no matter what route a developer takes, getting training, figuring it all out for one's self, or working with a vendor - the books and Web are essential.
The fastest route for a developer to get up to speed is to take one or more training courses. The cheapest way is to get the books and use the Web. The most expensive way is to hire an embedded Linux vendor. Of course, they all have other tradeoffs as well. Kevin Dankwardt K Computing ** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/ ** This list is shutting down 7/24/2004.