If you tried the follow the "how to get angstrom running" you will see in the sd set up area you will see how the mount points are set, if you follow the link for the for the linux boot disk format it will break down the process for using the command line.....
code.google.com/p/beagleboard/wiki/HowToGetAngstromRunning
I recommend you use gparted to reformat
Select the drive tab and select the sdb card
First delete all partitions so the disk is raw, apply changes
Second create a 74mb fat 32 for label use boot then create a ext3/4 partition with the balacance label use angstrom, apply changes
Third once finish right click on fat32 and manage flag check the box that's says boot
Now you should be able to cd into /media/boot or /media/angstrom
This has always worked for me as a quick. And easy meathod