I holed up in my cave with a Beagleboard XM rev B and spent the day learning how an ARM board boots. After a few hours of aimless wondering, misdirection, ill-conceived notions, and deep tangents, I am happy to say I managed to boot a minimal Yocto image on the Beagleboard XM!
beagleboard login: root
root@beagleboard:~# uname -r
The key difference (in terms of booting) between the Beagleboard and the Beagleboard XM is the lack of NAND. This changes the boot process slightly. Specifically, it requires an X-Loader and a u-boot binary on the MMC (as opposed to having them in NAND) - or something along those lines. I am thrilled that in a single day (not even a very long one) I was able to get Yocto booted on an architecture I have exactly zero experience with.
I will be spending next week tweaking poky recipes to generate the proper binaries and user boot scripts. The linux-yocto meta-data for the Beagleboard will also need to be updated for the new ethernet inteface on the XM. For those of you eager to boot Yocto on your Beagleboard XM, you won't have to wait long!
And in case you are wondering how your Kindle can help you with Beagleboard development, here are two ways. First, it can read the Beagleboard manual if you email it to your kindle account. And second, its power supply with the proper mini-usb cable provides adequate voltage and more current than my laptop and is able to power the Beagleboard XM, while my laptop could not source quite enough current, resulting in a kernel panic, oddly enough.