There's always tons of stuff shown off at CES each year. This year VIA showed off a prototype of 3.5" x86 PC that was running Linux. They're promoting it as an advanced PMP, but I could definitely using it as some kind of portable server.
The specs I could find on Gizmodo list the following:
Processor: VIA C7-M @ 1.0 GHz
Storage: 8 GB Flash
Display: 2.8" LCD
Resolution: 640 x 480
Dimensions: 8.5 cm x 8.5 cm x 2 cm
Weight: 150 g
Battery Life: 4 hours
Connectivity: WiMAX & WiFi
Video Codecs: H.264, WMV, RMVB, MOV, FLV, DIVX
I did some searching, but haven't been able to find any specs about RAM. However, this is still a prototype and isn't expected to be in production until 2009. Depending on the amount of RAM the computer ends up having, I could definitely see this being a nice little portable server to carry around—amongst other things.
Here's a nice little video from CES: