The following in the procedure I used to enable network booting from my Marvell Gigabit diskless MD.
Things you need to know: The driver name for your network card (for my nic its the 'sky2' driver) and the the device name assigned for your diskless machine (described later).
Follow the normal diskless installation http://wiki.linuxmce.org/index.php/PXE
until you get to the remote machine starting the boot process, but then fails with it unable to find eth0. This is happening because the initrd image that was compiled did not have the driver for your network card compiled in statically. This is normal as compiling in every network card becomes unruly and the image building process does allow for additional network modules to be loaded during the boot process. The installer that linuxmce uses builds this image from a base copy of the operating system (ubuntu) that is untar'd during the diskless setup process. It puts this into it's own directory that serves as a virtual harddrive for your diskless machine. In the /usr/pluto/diskless directory you should have a list of device numbers that correspond to your diskless machines. In my case '45' was the number for my diskless machine. Edit the file /usr/pluto/diskless/###/etc/initramfs-tools/modules and add on your nic's module. In my case I edit /usr/pluto/diskless/45/etc/initramfs-tools/modules and added sky2. Then run the /usr/pluto/bin/Diskless_InstallKernel.sh script with the device number (directory name) of your diskless machine. In my case "/usr/pluto/bin/Diskless_InstallKernel.sh 45". This script builds the initrd image and puts it in the proper place (symlinks it actually).
Reboot your diskless machine and it should come fine now.
Hopefully this will help people before they go out and purchase extra cards for their diskless machines that they don't really need. Perhaps the developers can support this in the future.