A Comparison of Solaris, Linux, and FreeBSD Kernels at OpenSolaris.org:

I spend most of my time teaching classes on Solaris internals, device drivers, and kernel crash dump analysis and debugging. When explaining to classes how various subsystems are implemented in Solaris, students often ask, "How does it work in Linux?" or, "In FreeBSD, it works like this, how about Solaris?" This article examines three of the basic subsystems of the kernel and compares implementation between Solaris 10, Linux 2.6, and FreeBSD 5.3.