Long story short, I use a Windows virtual machine on my workstation at work. I use qemu/kvm, and I use the user-mode networking stack for simplicity in setting up the VM. This trick should work with just about any virtualization package out there.
I wanted to be able to click a link inside the VM and have my browser on my host Linux machine open the link. I have no reason to run another browser inside the VM, and figured that it'd be nice to get this set up.
My host workstation is Arch Linux, and I use Firefox. From the command line, if I'd like to open a linux in firefox, I can run firefox <URL>, where <URL> is where I want to go. If firefox is running this opens the link in a new tab. This only works if two environmental variables are set: DISPLAY ...