I just hit the motherload! I found an MMC (Microsoft Management Console) snap-in called, conveniently enough, Shared Folders. Wow! This has everything. It shows all the shares, the individual sessions, and any open files (along with the user who has
them open). Nice!!! I haven't checked to see if this list is stays complete even if the mapped hard drives are missing as was my original criterial. but either way, this is where Phil's solution would work. Just go look at the backup to see what was being
backed up. That wouldn't fully work for me though, as I don't backup all of my server shares (ie the 2TB limit, I need to get a little picky about what gets backed up).
If you've never used MMC you're missing out on some great info. Just run MMC from the "search programs and files", then go to the file menu and press "Add/Remove Snap-in