localhost:hello chenzhen$ port search gcc
apple-gcc40 @5494 (lang)
    Apple's version of gcc 4.0

apple-gcc42 @5666.3_14 (lang)
    Apple's version of gcc 4.2

arm-aout-gcc @3.3.6 (cross, devel)
    gcc cross-compilers for arm-aout, with newlib runtime library.

arm-elf-gcc @4.7.3 (cross, devel)
    gcc cross-compilers for arm-elf, with newlib runtime library.

arm-elf-gcc3 @3.4.6_2 (cross, devel)
    gcc 3.x cross-compilers for arm-elf, with newlib runtime library.

arm-none-eabi-gcc @4.7.3_1 (cross, devel)
    The GNU compiler collection for arm-none-eabi

arm-none-linux-gnueabi-gcc @2005q3-2 (cross, devel)
    gcc 3.x cross-compilers for arm-none-linux-gnueabi.

arm-rtems-gcc @4.2.3 (cross, devel)
    gcc cross-compilers for arm-rtems, with newlib runtime library.

avr-gcc @4.9.1 (cross, devel)
    The GNU compiler collection for avr

localhost:hello chenzhen$ sudo port install gcc44

localhost:hello chenzhen$ port select --list gcc
Available versions for gcc:
  apple-gcc42
  llvm-gcc42
  mp-gcc44 (active)
  mp-gcc48
  none

localhost:hello chenzhen$ sudo port select --set gcc mp-gcc44