I stumbled across a few mp3s by jazz pianist Keiko Matsui at work... and WOW they are amazing. The quality on the mp3s is kind of crappy (128kbps just doesn't cut it for jazz) so I might buy some of her CDs.

Any recommendations on which ones are really good from anyone who has heard her work?

I have been a fan of Keiko Matsui's since... Wow, around 1996,
when someone got me Dream Walk (which I HIGHLY recommend,
by the way). You can check out the audio clips at Amazon--that'll
probably hook you. Once I got hooked, I backtracked and bought
her old CD's--basically all of them.

So, Dream Walk is a good place to start, although depending on
your taste, you'll like some albums more than others; Keiko's style
is varied, from dramatic "sound-track" sounding pieces, to quiet,
pretty--almost lullaby-like or melancholy songs. Next, get Sapphire
(again, listen to the clips on Amazon). It has some pretty jazzy
songs. However, you'll also find two songs with vocals--my least
favorite Keiko Matsui songs. For the most park, Keiko plays with
a band, and some of her pieces actually leave the piano to a more
accompanying position, leaving sax or other instrument to drive the
song, with generally nice results.

No Borders. A good album, and it has my favorite song "The Wind
And The Wolf" (a great dramatic song--listening to it evokes images
of a lone figure running at night through the rain against all odds.
In Keiko's concerts, her husband, Kazu, who plays the shakuhachi,
usually thrusts a fist into the air (spotlight on him) for dramatic effect
at parts during his performance of this song).

After that, if you're STILL intrigued, I'm sure you'll try albums for
yourself. :)

Good luck!
Brian