Ah, the weekend; it stretches out before you like an open field, waiting to be plowed into furrows of laundry, errands, home improvements and recreation. Of course, for us, recreation = new stuff for our beloved Macintoshes! Ready to load up that shiny new Airport Extreme with some capacious shared storage to hold your iTunes library? Let's see... mix one part Staples $140 closeout deal on 500GB Maxtor PATA internal drive, add in one part external FW/USB enclosure with wicked flame graphics for $30... result: one excellent drive that wouldn't look out of place alongside the Mystery Machine. If you prefer the MacAlly cases (rugged!), there's a free shipping deal on those too.
Now, for only $20 more you can have these guys assemble the USB-only case and drive for you, or these guys I've never heard of for only $145... but no pretty flames. Of course, if you want it to actually look good under the base station, then the Newer MiniStack is probably a better bet: the empty USB enclosure is only $60/$40 for an open-box unit, so add that Maxtor for some storage that's both functional AND stylish. Happy shopping!
Update: The trend of the comments is decidedly unfavorable towards the reliability of both the Maxtor drive and the Metal Gear case, so: message received. Here's a deal on a cheaper DiabloTek enclosure, which makes up for the extra you'll spend on a Seagate or WD drive. If you'd prefer a SATA drive, there is a Maxtor out there for a strangely low $127, as pointed out by Trojan below.