How much caffeine in tea?

Say what you will about David's Tea, I know not all their teas are good, I know they have been struggling financiall, but they do have their use. I found this picture and guide on their on their Facebook page. Now I can have a pretty good idea on how much caffeine content there is in what sort of tea. They also have an article on the subject on their website. Of course, it is calculated their brews, but one can easily extrapolate on their model. This will prove very useful when I want to know what I should drink as tea at what time of the day. It is also good to expand on my (rather poor) tea culture.