Well, these are the digital "current middle ages", now aren't they?
I use a Macintosh Titanium PowerBook G4 and Digidesign's Mbox, a new audio interface that is USB bus-powered. This means I can take this out into the field and actually record - at better than CD quality - direct to hard disk, even around the fire at night. No external electric power source needed.

My harp has a K&K "Big Twin" piezo pickup hidden inside. The Mbox has a pair of Focusrite preamps built in. Other than the small wire running out of the harp, there's no tip off visually, I try to keep the laptop out of sight. Pay no attention to the little man behind the curtain...