Search for PPPoE in the forum, and you will find hondreds of posts. Between those, you will find a link to a site of the man who ported some software to OSX to fix this.
And apple has stated that PPPoE will be in the Final release of OSX.
the best way of getting PPPoE if you have $150 or so to spend is to get a router that supports it (Netgear RT-311 or Linksys Etherfast are two that do.) Then the login is done in the router & you dont have to run any client program on your computers