National Boards Discussion Site?

Hello,

Does anyone know of some good National Boards discussion sites?

I have found a few on Yahoo! that are good, but they are becoming overrun with ads. I am interested in starting my own, perhaps through Ning (which is the online service for classroom2.0.com), but thought I would check to see if there is another out there that is good.

I am starting Nat. Boards in Career and Tech Ed next year and plan on using discussion boards A LOT.

Thanks,

Phil