I also read a book by Bob Serling that mentioned the power of licensing deals. Basically for you doing all the work, you get to keep 20% of any new revenues you generate. So if I can map out a good campaign online or offline, that might be viable as well. This idea is quite hazy though as I'm sure you can tell.
I would also like to hear more traditional upsells for design/agency businesses if anyone knows. I heard a training program on how to update the site is a good match. Any others?