You may want to do a search of the forum - this topic comes up often. I pasted my comments from an earlier thread below.
I have used the the King Schools test prep for my private, the Sporty's DVD course for my instrument and the ASA course for my commercial.
My thoughts are - the King stuff is purely test prep software. They prepare you to pass the written test. Their courses are not "ground supplements" on "how to fly". They are a bit corny, but they do a good job getting you ready for the written test.
Sportys was more like a ground school that had some test prep software built in. I liked the format much better that the Kings. Sporty's had much more detail on "how to fly" and that is what I wanted for my instrument rating.
The ASA Commercial program is more about passing the written but a lot cheaper than the King course. I don't think it is quite as good.
The Kings (John and Martha) prepared a course in conjunction with Cessna that is used at Cessna Pilot centers. I have heard some good things about it but have not seen it. (Jeff_S used it and I think he liked it).
My usual boilerplate - go check your local library. Mine had several shelves of videos and DVD's on flying. You can get a sample of several different courses.