As the Nucleo boards provide access to one of the STM32's USARTS (usually USART2) on their debug connector, this example shows you how to 'hook it' into the C library provided in the gcc-arm-embedded toolchain so that you can use printf and friends to talk to your board from your C code.
Add the object retarget.o to the OBJ files and it will add a constructor
function (SystemInit()) which will run before main is started. That
function initializes the system clock, the UART that is connected to
the Debug portion of the Nucleo board, and a 1kHz system "tick" interrupt
(which is useful for timing etc).
The main.c code simply prints out some numbers and creates a simple interactive dialog over the UART "console".
There are two board files now, one for the NUCLEO-F030R8 and one for
the NUCLEO-F411RE which differ by processor of course. The retarget file
is also updated to use scb_reset_system which more reliably resets the
board than hacking the stack does.
NB: As of this edit (12/12/14) you will need my additions to LOC3 to run this on the F0 or L0 Nucleo boards.