From a Senate source:

Sen. Reid: “Keep in mind, it’s approaching a trillion dollars.”
NYT: even the senators behind the compromise were uncertain of the number.
Roll Call: The uncertainty made it difficult to predict whether the final bill would be approximately $780 billion or $826 billion.
Fox News: about $811 billion in spending and tax cuts
AP: Democrats put the cost of the measure at $780 billion…Republican critics said that the price tag was actually higher…Official cost figures were not yet available.
AFP: The bill’s supporters noted that its price tag would be far smaller than the 937 billion dollars… Details were elusive… Republicans said their calculations put the new bill at roughly 830 billion dollars
LAT: a price tag of about $780 billion under the compromise deal, though the final figure was unclear.
Bloomberg: Democrats said the Senate plan totaled $780 billion while Republicans said that didn’t include the cost of additions made on the Senate floor including tax cuts aimed at helping the housing and auto industries.
Politico: While details are still incomplete, it appears the package, as initially brought to the Senate floor, will be scaled back…the total bill then would be in the range of $800 billion.
Reuters: Democratic senators agreed on Friday on a scaled-back $780 billion fiscal stimulus package
CQ: The deal would reduce the cost of the base bill by about $100 billion, to $780 billion, but this does not include spending and tax provisions added to the bill during Senate debate, according aides and senators. When those amendment are added in, Republican aides argued, the bill’s price tag is $827 billion.
Hill: a $780 billion economic stimulus plan