Well recorded solo piano and solo acoustic guitar?

Michael Hedges-Aerial Boundaries is excellent.

Chuck Leavell- Forever Blue

Solo piano:
Liz Story, any of her albums but I really like "Solid Colors" for setting a mood and staying there.
Also Carol Commune's "Intracoastal" is one of my favorites. Ran into her at a music store in Jupiter Florida a number of years back and found out that she was a wonderful solo pianist as well as a delightful person.
Newer is "The Chopin Project" by Ólafur Arnalds and Alice Sara Ott. This is available on LP, well worth the extra $$ over the CD, and is a wonderfully compelling performance and recording.
Solo Guitar:
Ted Greene "Solo Guitar", well recorded album and really really really stellar performance that stays in the same mood throughout.
Michael Gulezian "Language Of The Flame" is a masterpiece as well.
Enjoy!

Thanks, all, for the recommendations. I'm chasing them down one-by-one.

Slaw3: Which store in Jupiter? We're heading down there in a couple of weeks.

Egberto Gismonti..both solo piano and solo guitar. Great recordings.

Also, W.A. Mathieu - Available Light (solo piano)