My favorite by her is undoubtedly "Forgiven", for obvious reasons. After that, I love "Still", the acapella "Forgive Me Love", "Your Congratulations", "That I Would Be Good", "Unsent", and "Joining You". "Front Row" makes me smile (something to do with the movie/love metaphor), and I have a real soft spot for "You Learn".

...and her rendition of "Fake Plastic Trees" is lovely.