Triple boot (OS X/Win/Linux) via rEFIt doesn't work - Linux not visible in rEFIt

Here's what I've come across on my findings on doing something similar.

GRUB is a bootloader, it mainly accompanies Linux Distributions

In order to install Windows on the same drive you will need to make sure the partition mapping is MBR, as Windows can only be installed on that Partition Layout, this gives you a further problem, as Mac OS X can only be installed on a GUID Partition, Lion (10.7) checks for this upon Installation.

I would install Mac OS X, then BootCamp Windows 7, after this I would Install Linux with the Bootloader Installed on it's own partition.

You can then modify the Windows 7 bootloader to include GRUB detection on your partition so you can have a listing for Linux on your Windows Bootloader using EasyBCD. This will obviously create further work as you will need to boot your Mac then press the bootcamp boot key at the EFI boot screen, then choose Linux in the Windows Bootloader and then Linux in the Grub Bootloader. But this usually keeps everything separate, something I like.

I know you have already installed the other operating systems and are having trouble with Linux, but this is just my way to go around it.