Got it. Answer was contained in the page I referenced, under "to enable remote content sharing": http://www.microsoft.com/windows/win...ng.mspx#q20_17
The problem rested with Windows Media in my VMWare not wanting to share remote files. This is solved by editing the registry in Windows, which contains the library (list) of files.
So for future reference, here's a brief rundown if you want to share files to your Xbox 360:
1.) Share your directories on *nix via Samba, and make sure the directory is readable by everyone or by the "guest" account you'll specify in Samba. Make sure Samba is set to allow anonymous and guest browsing.
2.) Place Windows in a bridged-network Virtual Machine (VMWare) and install Windows Media 11. Add your Samba directories to the Windows Media library.
3.) Turn on your Xbox 360 and connect it to your LAN. Configure Windows Media Player to allow media sharing (under preferences) - you should see the Xbox listed automatically.
4.) Run "regedit" in Windows, and navigate to HKEY_LOCAL_MACHINE/ SOFTWARE/Microsoft/MediaPlayer/Preferences
(The following steps copied from Microsoft's website, cited above):
5.)Right-click HME, point to New, and then click DWORD Value.
Type EnableRemoteContentSharing, and then press ENTER.
Right-click EnableRemoteContentSharing, and then click Modify.
In the Value data text box, type 1, and then click OK.
6.) Restart Windows in the virtual machine, and in your media tab on the Xbox, hit music/video, and change the source to your virtual machine.