I’ve seen a number of lists of caffeine content over the years, but this is the most recent and, I think, most relevant. It lists content in standard serving size as well as per ounce for comparison purposes.
(Note – as an IT “professional”, I feel compelled to point out that this isn’t a database but a list. And as a fan of semantic markup, I should point out that this whole thing uses a table tag. Just to disclose.)