There are some HOWTOs out there in the net which describe some automatic network based install via PXE-booting a machine from a server which has a specific FreeBSD release in the PXE-booting area and a non-interactive config for sysinstall to install this FreeBSD version on the machine which PXE-boots this.
The setup of this is completely manual and only allows to netboot one FreeBSD version. The server-side setup for the clients is also completely manual (and only allows to install one client at a time, it seems). This is not very user-friendly, and far away from the power of Jumpstart/JET for Solaris where you create a template (maybe from another template with automatic value (IP, name, MAC) replacement) and can specify different OS releases for different clients and then just run a command to generate a good config for this.
I thought a little bit how it could be done and decided to write down all the stuff (so far 160 lines, 830 words) to not forget some details. All in all I think this could be done (at least a sensible subset) in a week or two (fulltime) if you have the hardware, motivation, and time. As always, the problems are within the details, so I may be off with my estimation a little bit (also depends upon the knowledge-level (shell, tftp, dhcpd, install–software) of the person doing this).
Unfortunately I do not know if I have the hardware at home to do something like this. I have some unused harddisks which could be used in a machine which is used temporary as a test-install-client (normally I use this machines as my Desktop… if I do not use my little Netbook instead, as I do not do much at home currently), but I’ve never checked if this machine is PXE-booting-capable (VIA KT133 chipset with a 3Com 3c905C-TX Fast Etherlink XL). I also do not have the time to do this (with the current rate of free time I would expect to need about a year), except maybe someone would call my boss and negotiate something.
I can not remember any request to have something like this on the freebsd-current, freebsd-arch or freebsd-hackers list since I read them (and that is since about at least 3.0-RELEASE). Is this because nearly nobody is interested in something like this, or are the current possibilities enough for your needs? Do you work at a place where this would be welcome (= directly used when it would be done)? If you use a simple solution to make a net-install, what is your experience with this (pros/cons)?