linux_ics is designed to make the process of sharing an Internet connection from a Linux computer easier for the average user. It handles configuring the interfaces, setting up NAT, and optionally running a DHCP server. In addition to Ethernet, linux_ics can also share an Internet connection over a WiFi interface in either ad-hoc or master mode.
otonat is a 1:1 NAT implementation for FreeBSD. Unlike other solutions that keep state for individual user connections even for 1:1 NAT, otonat is completely stateless as far as user connections are concerned. This allows it to scale much better and provide protection against misbehaving clients that may consume a lot of server memory by opening too many connections.