There's a blog post about the budget from OMB Director Peter Orszag, and you can download various parts of the budget or a 140-page document that can't possibly be the entire budget.
The theme of this budget (budgets always need a theme) is "A New Era of Responsibility." Said responsibility appears to cost somewhere in the neighborhood of $3.5 trillion.
The New York Times coverage of the budget.
UPDATE: A statement from House Minority Leader John Boehner, R-Ohio, who may or may not know the meaning of the word unprecedented:
The Administration’s proposed cuts, while welcome, don’t go far enough, and they appear to be a diversionary tactic – an effort to change the subject away from the unprecedented debt this budget heaps on future generations. Republicans will send President Obama our recommendations for further cuts in waste, but we’ll also be working to ensure these cuts don’t divert attention from the huge debt being piled on our children and grandchildren through this budget to pay for new programs and projects America cannot afford.UPDATE: I fixed the link.