I concur with Don about the fingering of the A chord. It all depends on the sound and the effect you want.

Personally, I favour the pinky on the second string, ring on the second and middle on the third, as I find that this facilitates the rapid "hammering on" of the second string and occasional forays onto the third fret with the pinky to give a quick transient Asus4, the sort of sound typified by Leo Kottke's playing.

The A chord described by Claymore does have its place in Travis/ Atkins type picking, but doesn't really lend itself to the more "earthy" styles of folk guitar imo.