Router - PFSense (beta 2.1)
pfSense with IPv4 and IPv6
I recently persuaded pfSense running on an ALIX based system with a Draytek Vigor 140 ADSL modem to connect up with IPv4 and IPv6 to AAISP. Here are some notes on how.
The example ALIX system I have is a bit pricey but it comes with pfSense already installed and three 100Mb interfaces. You can get just the board and do it yourself quite easily for a lot less. Make sure you have some way to access the RS232 based console in some way in case it all goes wrong if you use this box.
A very good alternative is an old PC. Either put several network cards in it or get a switch such as a Netgear 108 and learn about 802.1Q VLANs to make one NIC into several.