Small Business Tax Modernization Act of 2008 - Amends Internal Revenue Code provisions affecting small business taxpayers to: (1) allow an alternative standard tax deduction for the business use of a personal residence and establish a de minimis standard for determining personal use; (2) repeal restrictions on the depreciation deduction for cellular telephones and similar telecommunications equipment; (3) allow nonresident aliens to be S corporation shareholders; (4) increase the limit on the tax deduction for business meals and entertainment expenses; and (5) allow accelerated depreciation for energy-efficient heating, ventilation, air conditioning, or commercial refrigeration systems installed in nonresidential and residential rental buildings before January 1, 2012.