Wow this really is awesome.
After getting the new Linksys router I talked about last week, I connected up a new 2 TB Western Digital Elements Hard Disk to the router.
I was then able to share the hard disk without much hassle, it was pretty straightforward. Added security made it a little harder to work around (darn Windows network settings), but other than that it was smooth sailing.
So I now have a networked hard disk, where I can both read and write from my Windows AND my Mac machines. Awesome. It's plugged into the router, so if my Mac is on and Windows is off, but I want something shared... I can still just copy it over and turn on my Windows machine anytime later to get it.
All of this is amazing... but wait, it gets better. This is also a DLNA Media Server. So my Blu-Ray now recognizes the Hard Disk. This allows me to stream all of my music library from the HD to my TV entertainment center system, and I don't need to have any of the computers on in the house to do it. Sweeeeeeeeeet awesome.