You don't seem to know how tax brackets work.
Here are the tax tables, as of 2009.
2009 Tax Brackets Announced
The marginal rate refers to only income between those tax brackets.
The highest marginal tax rate is 35%, which kicks in only for income OVER $372,950. So, if I made $500,000 dollars last year, I would pay the following amount in taxes:
For the first $8350 dollars, I would be taxed 10% = $835
For the next $25600 dollars, I would be taxed 15% = $3840
For the next $48300 dollars, I would be taxed 25% = $12075
For the next $89300 dollars, I would be taxed 28% = $25004
For the next $201400 dollars, I would be taxed 33% = $66462
And for the remaining $127050 dollars, I would be taxed 35% = $44467.50
My total income tax, without any deductions would be $152683.5, which according to my math is about 30%.
Please show me a scenario in which someone could have a net savings by donating to charity.