It's interesting that all of these links talk about federal income taxes, but you talk about them as if they're talking about all taxes that people pay. Once you take into account payroll, sales, and sundry other taxes that people pay (many of which are pretty regressive), the system becomes much less progressive (it's still slightly progressive as a whole, but much less so than conservatives like to cast it).
This is one reason why Buffett suggests that we keep the 2% deduction in the payroll tax that President Obama proposed (and Congress passed) last year.
