@nudoru provided some links:
Garbage Collection Handbook
Azul pauseless GC
Azul in Managed Runtime Initiative (Linux)
SGen generational mono GC
Ruby On Rails GC optimization with preforking
.NET GC by Jeff Richter
.NET GC design doc on GitHub coreclr
Generational GC in Apache DRL
Writing a Simple Garbage Collector in C
Baby’s First Garbage Collector
Java’s G1 Garbage Collector
Garbage Collection Safepoints in LLVM
Java Garbage Collectors mini-book (Serial, Parallel, CMS, G1, Balanced, Metronome, C4 Azul, Shenandoah)