I actually just shared a list of 129 web 2.0s that Google indexes easily in the Jr. VIP section. I think that it's complementary to this thread. However, I don't think that web 2.0s work as well as they used to, and I think that their effect is going to be even weaker within a few months. There will always be some value to them, but look what happened to social bookmarking, link directories, article directories, etc. When a method becomes "standard SEO" and everybody and their grandmother is doing it, the effect is greatly diminished.
The real money making idea is to figure out what comes next, not replicate what people have been doing for the past 2 years