Laser diode packaging affects reliability, power level and weight (mass). Traditional thermal management materials - copper, copper/tungsten, copper/molybdenum, etc. - all have serious deficiencies. In the last few years there have been revolutionary thermal management material advances. There are now over 15 low-CTE, low-density materials having thermal conductivities that range from that of copper (400 W/m-K) to four times that of copper (1600 W/m-K). They are being used in an increasing number of commercial and aerospace applications. Some are low cost. Others have low cost potential in high volumes. Several are space qualified. This paper discusses the large and increasing number of advanced thermal management materials, including properties, applications, space qualification, cost, lessons learned, how to use composites to fix manufacturing problems, and future directions, including nanocomposites.