Setup the cross compiling environment

The one I used is Sourcery CodeBench Lite Edition, you can get it from its website
Please choose the eabi verison and format tar.bz2(I used arm-2008q3-72-arm-none-linux-gnueabi-i686-pc-linux-gnu.tar.bz2)
Untar the file

$ mkdir ~/overo-standalone
$ cd ~/overo-standalone
$ tar xvjf arm-2008q3-72-arm-none-linux-gnueabi-i686-pc-linux-gnu.tar.bz2

Add the bin to your PATH

$ export PATH=$PATH:~/overo-standalone/arm-2008q3/bin

Write the program

The following two Hello World program has been tested on an overo
You can play with them

Compile the program

Assembly verison

$ cd asm/

Use make to compile the asm program

$ make

Boot.asm

C version

$ cd c/

Run the compile file in c program folder

$ sh compile

Run the program

You needed a flashed, bootable MicroSD. You can make one by using Sakoman's scripts (mkcard.sh and mksdcard.sh)
Copy the .bin file generated by the compiler to the boot drive on the SD card

$ cp *.bin /media/boot/

Umount the SD card

$ umount /media/boot
$ umount /media/rootfs

Plug the SD card in overo and connect the overo on a Tobi expansion board
Power it up and go into serial console
When the console prompt "Hit any key to stop autoboot", please hit any key

# mmc list
# mmc part
# fatls mmc 0:1
# fatload mmc 0:1 0x80200000 uimage
# go 0x80200000

By now you should see "Hello world!" poping in the console