I use Orville Redenbacher's natural "simply salted". The oil they use tastes just like butter in my opinion, but they don't use any.
To find plain bagged popcorn is usually a pain in the a**. It seems Newman's organics doesn't even have just salted. They have one that's 99% 'fat free' unsalted, but I think it still contains a touch of butter, maybe. It didn't taste like there was anything on it.
I wish I could just get an air popcorn maker and buy some organic popping corn so I could just eat healthy stuff, while knowing there are no animal biproducts involved. sweatdrop