One for the geeks:
Sometimes, after a friend/family type person has been convinced to throw out their crappy old Windows9x PC and get a Mac at last, they come back to me with the old "Could I still use my old PC for something? - I don't want to throw it away" question. Or sometimes I get asked "is there a cheap way that I could have somewhere to store files/data?".
I have two solutions that I like to roll out here; one is to buy an external USB2/Firewire disk, and the other (lower-cost) answer is to use that crappy old PC as a home network server. The home network server would, of course, run Linux as it's rock-solid stable, reliable, and most of these types of users are too scared by command lines to do anything to harm their own server (as opposed to using Windows as a home server, which is invariably infested with crap within a few weeks).
One of the troubles with Linux (and I'm happy to accept that there are some, still) is that Webmin is about the only interface that is even remotely friendly for a non-techie to use to administer their home file server, and installing and configuring Linux (even a pared-down install) and Samba and configuring webmin takes an evening of my time.
Now, I'm not saying that I'd move away from Linux at home - I like the flexibility too much, but for a quick and dirty pure file server on old PC hardware, I have recently been very impressed with the BSD-based freeNAS. The install is a bit bumpy, so granny can't do it herself yet, but it is lightweight and fast and supports the whole gamut of network protocols (including SMB, FTP, NFS, SSH and AFP) and is administered purely via a web browser. Furthermore, you can run the O/S from a USB key and use multiple internal disks for software RAID storage.
It will require further investigation before I'd trust it enough to recommend whole-heartedly (how does it deal with failed disks? how can we back it up? if the O/S dies can we get our data back from the storage disks easily?, etc), but from the 10-minute play I had with it, it looks good. :)