So - here's the rough steps without a specific walk through of each one, except for reinstalling grub, which is really the crucial step to getting everything to hum and purr along nicely. The caveat is that this worked for me, on my system, it might not work on yours - so take precautions, backup, verify backup, store a backup off-site - you know the drill, I shouldn't need to tell you.:
1) Install Windows 7 Easy enough, follow the prompts and pop Windows 7 on your machine.
2) Install Linux Choose your flavour - I've got Mint up and running, but go for Ubuntu if you prefer. Actually, go for pretty much whatever you want. Ubuntu and Mint will give you a nice trouble-free install of Grub to dual boot your system. It should work out of the box.
3) Create a VHD in Windows 7 and use that space to install Windows 8. Check out Scott Hanselman's great blog posts on this because it takes you through in detail what you need to do. Pay attention, because it's subtle (How to guide to installing and booting windows 8 consumer preview off a VHD and Guide to booting windows 8 developer preview of a VHD)
4) Boot up into Windows 8. Crap your pants a little as you notice the Windows 8 boot loader has made your Linux install disappear.
5) Boot to Linux with a live CD and re-install Grub manually. This is fairly simple - once booted, bring up a terminal and do the following (obviously, you need to know your partition number that you've got your linux install on - mine's sda6 - I have sda1 and sda2 as system recovery and windows recovery, sda3 as my Windows install, sda4 is a logical partition, sda5 is swap, sda6 is my actual Linux mint):
sudo mount /dev/sda6 /mnt sudo grub-install -root-directory=/mnt/ /dev/sdaNote that the second line has the number left off the "sda" on purpose. PAY ATTENTION!
6) Re-boot - you should have options for Linux and Windows 7 again. On my system, selecting Windows 7 takes me to the Windows 8 bootloader from whence I can choose either Windows 7 or Windows 8 for boot.
Now this isn't perfect, because I have 2 boot menus, but you know what? It will do for now.