As described in the Ångström web page:
Ångström is an effort to make a stable and userfriendly distribution for embedded devices like handhelds, set top boxes and network-attached storage devices and more.
A great tool for embedded engineers and the one that will be used through the beagle-ros project. Getting started with it is actually quite straight forward. You just need to have bitbake in your computer and run:
git clone git://github.com/Angstrom-distribution/setup-scripts.git cd setup-scripts ./oebb.sh config beaglebone MACHINE=beaglebone ./oebb.sh bitbake systemd-image
After the process is completed you should have under setup-scripts/build/tmp-angstrom_v2012_12-eglibc/deploy/images/beaglebone the files needed that should be put in the microSD (use mkcard.txt for that purpose).