There are many systems of wisdom left behind in the wake of civilizations that have  proceeded us on this planet.  I have deemed it a priority in my life to learn as much from those traditions as I possibly can.  At the left are links to those I have found to be of the greatest value.  There are many others especially in the Western tradition that have drawn my attention; most of those are based on belief and that in my opinion is a  retarding error in spiritual growth--difficult to avoid, but essential to avoid.  If   you meet the Buddha in the road--kill him.  Full stop.  Ne Plus Ultra.  Momenti Mori.  Remember we must die.