U-Boot/Legacy U-Boot

Initially developed by Tom Cubie and now developed and maintained by Henrik Nordström the u-boot support comes in two branches, one with NAND and android stuff(boot.img, fastboot) support and another with MMC-only ( aka SD ) support, which is more the traditional linux style.

Tutorials
How to remove the old environment from a card:  card=/dev/sdc #/dev/mmcblk0 dd if=/dev/zero of=${card} bs=1024 seek=544 count=128