I have a regular-size bosu that my sister bought me for my birthday. She says it was $100 and I love it. I haven't really seen one cheaper than that but I think it is worth it.
I have several DVDs for the Bosu. My absolute favorite is "Awesome Strength" by Mindy Mylrea. She uses the bosu for the entire workout which consistents of strength training, cardio, abs and balance.
I also have "Bosu Total Sports Conditioning" also with Mindy Mylrea. It consists of general sport movement patterns, practice drills and strength and cardio drills.
The third DVD I have is "Body Bar and Bosu Training". There are two workouts on this DVD. One is a beginner/intermediate workout and the other is intermediate/advance workout. This uses both the bosu and a body bar and is very challenging.
Jean Louise