International Tax Simplification Act of 2006 - Amends the Internal Revenue Code to revise rules relating to foreign income and income earned by controlled foreign corporations (Subpart F income), including to: (1) make permanent the active financing exemption for qualified insurance income and the look-thru treatment applicable to related foreign corporations; (2) eliminate foreign base company sales and services income and oil related income from foreign base company income; (3) repeal certain rules for the application of the foreign tax credit to foreign oil and gas income; (4) extend from 10 to 20 years the carryforward period for excess foreign taxes; (5) accelerate from 2008 to 2006 the election to allocate interest earned by an affiliated group of corporations on a worldwide basis; and (6) increase to $5 million the tax exclusion for foreign base company or gross insurance income (de minimis rule).