Arm binary level calling conventions come in three incompatible flavours. Hardware stays the same, but libc/linker etc are not compatible due to different calling convention. Code compiled on one version will generally fail on another version.
Arm - OABI. The old one, and the one openmoko OM2007.1.
Arm - EABI. The new one, used by OM2007.2 and later versions. Should be slightly faster. Angstrom distribution also uses this. (See http://www.angstrom-distribution.org/unstable/images/fic-gta01/20070524/ )
Arm - big endian.