I ran across a book at the Library the other day that might be of interest to some of you.
It is
Improvising Jazz by Jerry Cocker. Its available at Jaime Aebersold's Jazz site:
Jazzbooks.comIn the back, there are several pages of common progressions as they occur in actual music (at least as of the 1970s). The advantage of working with these is that they involve different harmonic rhythms. Rather than playing each chord in a progression pattern for the same duration, some will last longer than others -- just as in regular music.