De Anza flea market for $5. I poked around with it a little bit at the time, but couldn't get it to do much, assumed it was DOA, and tossed it in one of my parts boxes.
Geode processor. The Geode had a very short-lived life at National Semi before being bought by AMD and spending the rest of it's days as AMD's low-power x86 core (Which was originally going to power the OLPC project before that project turned into a cluster, for a variety of reasons), so seeing one in the wild and getting it running was an interesting challenge.
RDP client. RDP is a proprietary Windows protocol which seems not to have such good Linux support. Luckily, in addition to being an RDP client, this ROM also includes... a web browser...
IDE/PATA is a 40 pin connector, plus the four pin Molex power connector standard in computers before SATA and PCIe showed up and complicated matters. The 2.5" IDE spec is identical, except designed for laptop hard drives; A 2mm pin spacing instead of 0.1", and an extra four pins at the end (41-44) for power and ground.
CF card. CompactFlash cards use a 50 pin interface, which supports a mode which is signal compatible with PATA. This is why you can get adapter cards from CF to IDE on eBay for $3; they're just two connectors and a voltage regulator.
Of course, right-angle female 2.5" IDE to CF adapters only come in one orientation. Any bets on which direction it is? Thaaaat's right - the wrong way. The power supply prevented it from fitting, so I de-soldered the 2.5" IDE connector, flipped it, and jumpered everything back into place.
Would you believe that the Ubuntu installer requires a 686? They call it x86 or i386, but no, you MUST have a 686 to boot Ubuntu. Would you also believe that this ancient Geode processor is only a 586. The Ubuntu installer somehow manages to use some instruction set which makes the difference between the 586 and the 686. This seems kind of silly, because pretty much every revision of the x86 since the FPU migrated on-chip on the 486 has just been proving exactly how complicated you can make a CISC, but bloat does seem to be the Ubuntu way these days...
I think I might use this system to replace my Chumby as my always-on server, since my 170W file server is a little expensive and loud to keep running all the time. This thing has comparable specs with the Chumby, with the added advantage of an actual serious operating system (I am getting freaking tired of dealing with Busybox). 300MHz should be plenty to run my TFTP server, printer server, etc on my LAN. Running my SLO print server off a National Semi x86 would be a nice compliment to the 186 running my parent's print server.
The one thing I'm stuck on now is this 80 pin unpopulated connector labeled PCI next to the power supply. Desktop PCI has more than 80 pins, but presumably this is for miniPCI. I'll need to do some more research on exactly what the pinout should be for an 80 pin PCI variant, and then bodge-wire in a useful expansion card.
For your amusement, I give you the contents of /proc/cpuinfo. Notice how the flags for supported instruction sets is about a fourth of what you see in modern CPUs: