Typically, people who ask this question have two PC's at home, one with FreeBSD and one with Win95; the idea is to use the FreeBSD box to connect to the Internet and then be able to access the Internet from the Windows95 box through the FreeBSD box. This is really just a special case of the previous question.
... and the answer is yes! In FreeBSD 3.x, user-mode ppp(8) contains a -nat option. If you run ppp(8) with the -nat, set gateway_enable to YES in /etc/rc.conf, and configure your Windows machine correctly, this should work fine.
More detailed information about setting this up can be found in the Pedantic PPP Primer by Steve Sims.
If you are using kernel-mode PPP, or have an Ethernet connection to the Internet, you will have to use natd(8). Please look at the natd section of this FAQ.