Which BSD?

[AZ_Pete]

Hello All,
I don't know if this is the place to ask, but I have seen other BSD threads
floating around, so I thought I start here.
I have a spare box I would like to start playing with BSD to add to my Linux
network at home.
However, I don't know which BSD to try: OpenBSD, NetBSD, FreeBSD.
What are  the differences among them?  Any Recommnedations?
Any help would be appreciated.

The hardware is: AMD K3-450, 128MB Ram, 9GB IDE HD, 3Com NIC, AGP VGA.

Peter