Make sure the drive is GUID.
Download any of the latest Linux Live CDs (Ubuntu, Red Hat /Fedora, etc.). Torrent downloads are also available. Burn the iso to a cd. Boot to the live CD.

Use that to repartition using gparted. (System->administration-Gparted)
Linux should be around 8G. The rest is up to you. Partition format is unimportant.

Install W7
Install OSX (see OP)
Install Linux. Linux will install grub and run grub-config automatically which will do an os-probe and ALMOST do the right thing.

Remove CD, boot into Linux, find out which partition has OSX. I use GParted which can be installed using:

sudo apt-get install gparted

Keep gparted around; it is useful!

edit the /boot/grub/grub.cfg file

Add in the custom section at the bottom of the file:

menuentry "Your name for OSX" {
insmod hfsplus
set root=(hd0,6) # your disk /partition may be different
multiboot /boot
boot
}

You must use the custom section else an os-probe will over-write the information. Remove all the other menu entries for OSX in the grub.cfg file; they don't work because they assume a mac efi system. Save the file. You must be root or must do sudoedit to edit and save properly.

If, while booting, you don't see the boot options, you should hit the ESC key when the grub message comes up.

Life saver: the Linux dd command. Installing Windows 7, OSX, multiple times can be a pain. I have used the Linux dd command to save the disks and partitions. Then it is just a matter of copying them back if I messed up. This is not the right forum to go into dd though.

The only issue I have with grub is it does not have a sweet interface like chameleon.

And remember, experiment. Once you are done experimenting, put in a second disk (about 3x the OSX partition) and use the time machine to save your work and you will be happy. It tastes better than icecream.