The New Teacher Project (TNTP), founded in 1997 by teachers, is a national non-profit that has been integral in a number of key policies and initiatives including Race To The Top. They are also behind the Teaching Fellows program which is designed to recruit and support highly effective, new teachers.
In July 2012, TNTP published a report titled The Irreplaceables which I found to be informative and inspiring. This month, they have published a report titled Perspectives of Irreplaceable Teachers which takes the idea of retention even further in an effort to identify the perspective of only the best teachers.
Each report is linked below and I would encourage you to read them both (in your spare time).
Perspectives of Irreplaceable Teachers, August 2013