Now pfsense release version 1.2.3 .It only support 1 interface use PPPoE.But with pfsense 2.0(Beta 4)you can use multi interface use PPPoE and Version 2.0 change config load balance outbound.So I will intro to you config multi interface use PPPoE.
II/Install Pfsense as previous Document
III/Config multi interface use PPPoE config as images
Note:you can create PPPoE Server for test this document with pfsense
IV/config load balance with pfsense
As previous version (1.2.3) you can config as http://conheotiensinh.blogspot.com/2009/10/multi-wan-load-balancing-outbound-use.html.But with pfsense version 2.0 load balance outbound change config.
step1:config gateway (system ->routing) config 2 gateway as images with 192.168.127.128 and 192.168.128.129 IP of PPPoe server (it will auto detect when connect via PPPoE)
step 2:config groups(system ->routing) change to Groups tab and create group as image
Step 3:view status of Gateway and Groups when 2 line connect
Step 4:Test disconnect 1 interface and view status
Step 5:create rule as image