Eric Dolphy's first few albums are a good starting place if you're looking to check out jazz stuff. His music is a great balance between the structured bebop of the 40s and 50s, and the free stuff that came in the 60s. Also, Ornette Coleman's "Shape Of Jazz To Come" and "Change Of the Century" are in the same mold. It's not the apparent free-for-all that "Free Jazz" is-it has noticeable structure and basically standard rhythms, but the melodies are alot more free.
And Miles Davis "Kind Of Blue" of course.