OnLamp's FreeBSD vs. Linux high level differences: runlevels, startup, kernel updates, software installation, documentation.

OnLamp's More FreeBSD vs. Linux: installing bash, modifying user accounts, creating user accounts, device names, sysctl, modules, & terminology.

http://www.over-yonder.net/~fullermd/rants/bsd4linux/bsd4linux1.php is more philosophical than how-to

The Linux Binary Compatibility chapter of the FreeBSD handbook.

http://linuxhelp.blogspot.com/2005/11/linux-users-perspective-in-installing.html A Linux User's perspective in installing FreeBSD 6.0

http://www.burdell.org/articles/freebsd/ A guide for Linux users wanting to explore FreeBSD.

FreeBSD's own comparison with Linux

http://www.freebsddiary.org/linux-users.php