Donovan's version has always been my favorite. I used to listen to Donovan sing it from his album over and over again. Of course I am a huge Donovan fan and love all of his folk ballads.
Also love Judy Collins version as well.

The group Golden Bough from Northern, California (now living in Oregon I believe) did a very nice version on one of their older albums.
I have seen them in concert several times over the years and they have a lot of albums.

Folksinger, Larry Siegel has a good version as well.