When we got our microwave (about ten years after everyone else... we're rather slow when it comes to acquiring new consumer goodies) I went out and bought a bunch of different brands of microwave popcorn. It sure was convenient and made the entire house smell like a movie theatre, but then I read the ingredients... Oh My, What Garbage Americans Will Put In Their Mouths!
So I dumped the remaining bags of toxic waste and purchased a Presto PowerPop. It is a popcorn popper that is designed to work in a microwave. It cost between $15-$20. The PowerPop comes with a package of PowerCup "microwave concentrators" that improve the popping efficiency; they are round cardboard thingies with embedded metal rings that sit in the bottom of the popper. You can use the PowerPop without them, but they really do decrease the number of unpopped kernels to near zero, so the minimal ongoing replacement cost is worth it in my opinion. They last for multiple uses, particularly if you don't use oil with them.
The difference in cost between using the PowerPop and microwave popcorn is dramatic, so the PowerPop pays for itself in a short period of time. We recently stopped using Orville Redenbacher's popcorn after I discovered that ConAgra owns the brand (we try to avoid supporting monopolistic multi-national food corporations in our house...) so we switched to organic popcorn from our local food co-op. Now we are 100% organic... Sorry Orville, wherever you are!