This page is how to recover ("unbrick") a broken BeagleBoard. It should help you if you messed your boot configuration and BeagleBoard doesn't boot any more the normal way ("bricked").
What has happened?
Depending on user button OMAP3 on BeagleBoard uses different boot order. Normal order if user button isn't pressed at power up is boot from
NAND -> USB -> UART -> MMC
in this order. Depending on the boot medium (e.g. MMC) this might fail if something bad is in NAND flash which confuses OMAP3 bootrom thus stopping it to reach MMC boot stage.
This might happen if you e.g. mess your NAND, e.g. something went wrong using Steve's NAND flash procedure.