I think Rod Machado has some good products. Some would say that his method of adding in silly items is a distraction, but he is able to pack a lot of information into his books and videos. I haven't done his ground school online class but I have purchased some of the specific area videos and I think they are all pretty good. You can watch them many times and they include quizzes on the material. I've noticed when I re-watch these videos that I sometimes missed some of the specific items mentioned when I watched it the first time. I would bet that his Private Pilot Ground School is pretty good too. I actually wish I would have purchased it, but I'm past that point now.
I did purchase the Sporty's Ground School a while ago and I didn't think it was that great. There is a lot of information that has to be packed into these classes and its not that easy to do an all encompassing job.