Writer’s Digest recently offered a webinar on how to plot a novel by the Plot Whisperer, Martha Alderson, that I found very helpful. Alderson has a YouTube channel with 27 short videos for each step of the process.
The first video in the series is below (she says to ignore the barking dog in the background).
If you’d like to view more of her videos, her YouTube channel is: http://www.youtube.com/user/marthaalderson
And the remaining 26 videos for her plot tutorial can be found here.