Thousands of houses were destroyed in Gaza during the fighting
International donors have pledged almost $4.5bn (£3.2bn) in aid to the Palestinians, chiefly to rebuild Gaza after Israel's recent offensive.
US Secretary of State Hillary Clinton said Washington would donate $900m, and vigorously seek to advance peace.
Palestinian leader Mahmoud Abbas told a summit in Egypt cash was "insufficient" without a political solution.
Israel, which has been fighting Gaza militants, refuses to allow building materials into Gaza for reconstruction.
As well as the $900m promised by the US, Saudi Arabia pledged $1bn (£703m) for Gaza.
Egyptian Foreign Minister Ahmed Aboul Gheit says the total of $4.48bn from about 70 countries was "beyond of our expectations".
Hillary Clinton announces US pledge
The Palestinian Authority had requested only $2.8bn (£2bn).
Mrs Clinton told the conference in the Red Sea resort of Sharm el-Sheikh: "Our response to today's crisis in Gaza cannot be separated from our broader efforts to achieve a comprehensive peace."
During her first visit to the Middle East as top US diplomat, she said the aim of the aid was to "foster conditions in which a Palestinian state can be fully realised".
Some 1,300 Palestinians, of whom 412 were children, were killed and thousands of homes and businesses destroyed in December and January as Israel tried to bring an end to cross-border rocket attacks by Palestinian militants.
'Visible signs'
Hamas, which controls Gaza but is regarded by both the US and the EU as a terrorist organisation, was not invited to attend the one-day conference.
Development efforts will remain insufficient, powerless and threatened in the absence of a political settlement
The movement welcomed efforts to rebuild Gaza but said it should have been asked to take part.
Hamas spokesman Fawzi Barhoum also told the BBC that donors had "politicised" aid by handing it to Mr Abbas's Palestinian Authority.
Mr Abbas said that while all the support was appreciated, "we insist on the pressing need to achieve substantial progress towards a just settlement [of the conflict with Israel]".
"The reconstruction and development efforts will remain insufficient, powerless and threatened in the absence of a political settlement," he said at the conference.
British Foreign Secretary David Miliband said that "visible signs of progress" in the West Bank and Gaza were vital.
He added that Palestinians needed "a single government across the occupied territories" - a direct appeal for rival Palestinian factions to put aside their differences.
French President Nicolas Sarkozy, for his part, urged Hamas "to engage resolutely in searching for a political solution and engage in a dialogue with Israel".
Aid flows
Raising money for Gaza is the easy part, the BBC's Christian Fraser in Egypt says.
The real business of the conference is the practicalities of how to get it to the people who need it most, he adds.
All but essential supplies are still subject to Israeli blockades at the crossing points into Gaza.
Building and raw materials deemed by Israel to be useful to militants as well as civilians have been banned.
Aid workers say items turned away at the border have included macaroni, lentils, paper and school books.
Mr Ban described the situation at the crossings as "intolerable".
"Aid workers do not have access. Essential commodities cannot get in. Our first and indispensable goal, therefore, is open crossings," he told delegates.
But he said it was also "essential" to ensure that illegal weapons were prevented from being allowed to enter Gaza.
Donor countries as well as Israel, which did not attend the conference, have stressed that they do not want aid to end up in the hands of Hamas.
"Like the international community, Israel does not want to see support to Hamas," Israeli government spokesman Mark Regev said. "We want to see support for the people of Gaza."
The Palestinian Authority has proposed that all aid to Gaza should be channelled through itself.
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Development efforts will remain insufficient, powerless and threatened in the absence of a political settlement
'The world has failed our nation'
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