I wanted to comment on "Practical BeagleBoard" above. This book was posted by Apress by mistake.
In fact, the book does not actually exist yet - I am the author and I haven't finished writing it yet. It should be ready in late spring 2011 (Note: it will not be published by Apress.) I apologize for the confusion. Please feel free to contact me with any questions.
As a further comment, I also highly recommend Chris Hallinan's Embedded Linux Primer, for which the 2nd edition was just released. It is an excellent introduction to embedded Linux, and to embedded systems programming in general.
Thanks,
Jeff Osier-Mixon