From their 2006 10k Notes to the financial statements, filed with the SEC:
2006
Income, sales-based and all other taxes and duties totaled $100.7 billion in 2006, an increase of $2.1 billion or 2 percent from 2005. Income tax expense, both current and deferred, was $27.9 billion, $4.6 billion higher than 2005, reflecting higher pre-tax income in 2006. The effective tax rate was 43 percent in 2006, compared to 41 percent in 2005. During both periods, the Corporation continued to benefit from the favorable resolution of tax-related issues. Sales-based and all other taxes and duties of $72.8 billion in 2006 decreased $2.5 billion from 2005, reflecting the tax impact of net reporting of purchases and sales of inventory with the same counterparty, only partly offset by the effects of higher prices.
JG, to answer your question as to why they are paying such a high rate - $6 billion of those taxes appear to be paid to non-US entities, at a rate higher than US rates... Nice catch! Here is their income tax reconciliation, required on the notes to the financials:
note - the chart came out screwy...