Within the official Debian archive there are or have been four different ports to various flavours of the ARM architecture:
ArmPort - the first port, using the "old" (now obsolete) ABI (OABI). First released with 2.2 (Potato), last released with 5.0 (lenny). GNU Triplet: arm-linux-gnu
ArmEabiPort - newer port using the "new" ABI (EABI), supported on ARM v4t and higher. First released with 5.0 (lenny). GNU Triplet: arm-linux-gnueabi
ArmHardFloatPort - the latest 32-bit port, using the hard-float version of the "new" ABI (EABI), targeting ARM v7 and up. First released with 7.0 (wheezy). GNU Triplet: arm-linux-gnueabihf
Arm64Port - the latest port, for the 64-bit ARMv8 architecture. Will be released with 8.0 (jessie). GNU Triplet: aarch64-linux-gnu
There are or have-been at least two unofficial ports outside the Debian infrastructure.
Raspbian - Uses the hard-float version of the "new" ABI (EABI) like Debian armhf but targets v6 rather than v7. Currently tracks Debian wheezy and jessie. Primarily but not exclusively targeted at the Raspberry Pi. GNU Triplet: arm-linux-gnueabihf
- armeb - Big-endian OABI port targeting the linksys NSLU2 and similar. Interest fell after a method was determined for running little ending Linux systems on the NSLU2. Active during the sarge timeframe and now abandoned.