RealGM has a good article on the 1971-76 Celtics, who it calls the most underappreciated of the great historic NBA teams.  There have been 7 teams in NBA history that over a five year span both won at least two titles and averaged at least 58 wins a year.  The Celtics of the '60s and '80s, the '80s and '00s Lakers, the '90s Bulls, and the '00s Spurs.  And the '70s Celtics, coached by Tommy Heinsohn.  The article points out the interesting fact that of the top seven guys on the team, five went on to become NBA head coaches (Don Nelson, Paul Silas, Dave Cowens, Don Chaney, and Paul Westphal).  The article also makes a good argument for Cowens as one of the most unjustly forgotten players in league history.

http://celtics.realgm.com/articles/362/20080807/that_70s_show_shining_light_on_the_most_underappreciated_team/