I have a question...when using multiple partitions for shared access, do you use '/media/' as the mount point, or is there a different way to set this stuff up? I'm setting up a multimedia system that dual boots Ubuntu and Win7 off of a single 1TB drive, and has a 1TB as a slave for music, games and pics, along with a 2TB slave for movies and shows. The only thing I really know about mount points for shared partitions is that my Windows partition mount point is '/media/OS' And that the Partition label is 'OS'. Aside from that, I've never tried to set up slaves under Ubuntu. I've done it under windows, but, I know that's another animal entirely.
You can actually use single HDD for dual booting without any issue, because both OS will be installed on different partitions.
And as far as mount point goes, you should be able to use "/" as your mount point. This little old but very good official help should give you better idea about partitioning in general in Ubuntu.