I have a few.. I have 3 partitions on my main system, plus network drives mounted from my server (sooo much easier to store data always as the D: drive)

So, to list:
c: (os)
d: (mount: data)
e: (mount: download scratch drive)
f: (mount: download archive)
g: (mount: complete downloads)
i: (mount: media drive)
k: (local partition: vmware and some other stuff)
l: (mount: server temp drive)
v: (CDRW - actual)
w: (daemon virtual dvd drive)
y: (daemon virtual dvd drive)
z: (Local partition: fat16 drive with dos apps, just in case)

So; 12.

Now, that being said; I monitor free space, shortcuts, etc all from a samurize config that can be integrated into any theme.

deuce: That's how I started, before I got the server ;)