The average US home now receives an average of 104.2 channels of television, according to Nielsen Media Research. And at any given time, 72 of those channels are showing an abs-workout infomercial.

All kidding aside, the increased number of channels is important because the number of channels tuned in to increases with the number of channels available. The average household tuned in to 15.7 channels for at least 10 minutes each per week in 2006, meaning that at least 15% of those 104.2 channels are getting watched with more than a glance.
The study also reported that 30-second commercials still dominate TV advertising, and represented 57% of all commercial units in 2006.
The number of shorter 15-second commercials decreased in primetime but increased slightly in daytime. The total number of commercial units dropped 2% in primetime and 2% in daytime.
Other findings in the study included the number of US TV homes (111.4 million), the average number of TVs per household (2.8) and the percentage of US homes with DVD players (84%).
Via eMarketer
