The following document includes some basic and effective stretches for the Shoulders. Included is variations for differing levels. As always there are additional things that could be added in to any health shoulder program. One is simply adding these into your daily regimen of stretching. Another is doing joint mobility drills such as rolling the shoulders, swimming motions, etc. that take the joint through active and various ranges of motions. Third, one can add in simple strengthening exercises from pressing, to side/lateral raises and more commonly rotator cuff exercises.
Hope this guide helps and if you have any questions please feel free to email. Also, please feel free to share this guide with anyone you feel can use these stretches.