Millions of Sudanese still live in fear of violence, a year after the peace deal ended 21 years of war between north and south, aid agencies say.
Some people have already gone home after the end of the war
Many Sudanese have little to celebrate because of conflict in the western province of Darfur and insecurity in the south and east, they say.
And communities in the south still lack food and water, despite pledges made by donors last year to provide $4.5bn.
However, some 500,000 southern Sudanese are expected to return home this year.
At a ceremony to mark the anniversary in the main southern city of Juba, the former rebel Sudan People's Liberation Movement has admitted that the peace agreement has accomplished very little.
"The challenge this year is to make sure that people of Sudan really feel the benefits of peace," said Sorcha O'Callaghan, spokesperson for a coalition of international aid agencies.
The coalition urged donors to fulfil the pledges they made in Norway last April, saying that unless the hopes and needs of Sudan's people are met, the time and effort spent in negotiating the peace deal agreed will be squandered.
The United Nations special representative in Sudan, Jan Pronk, has said that although the peace agreement is still holding, the division of Sudan's oil revenue remains a major hurdle.
In the agreement provision was made for South Sudan's oil wealth to be shared equally between the Arabic, Muslim north and the mainly Christian and animist south.
Sudan analyst Peter Moszynski told the BBC News website that the government in the south is getting far less oil money than it had expected a year ago because of disputes over whether some functioning oil wells lie in the north or south.
Mr Pronk said an organisation like the International Monetary Fund should resolve the dispute.
The peace deal was hit by the death of long-time southern rebel leader John Garang just three weeks after he had been sworn in as Sudan's vice-president.
"The peace dividend has not been delivered. There is very little sign of change in the south outside [the main towns of Juba and Rumbek]," Mr Moszynski said.
"People talk about reconstruction but in reality there was nothing there to start with."
Rebecca Dale from the International Rescue Committee said that some of those who have returned to their homes in south Sudan have since returned to the capital, Khartoum, because they found so little infrastructure.
She said that 25% of children in the south die before they reach the age of five, there are very few schools and there is only one doctor for every 100,000 people.
Mr Moszynski said that the disputes in Sudan were far more complex than realised by the international negotiators who pushed north and south to reach a deal, ignoring the problems in Darfur.
After six years of autonomy in the south, a referendum is due in which southerners are due to vote on whether they should secede or remain part of Sudan.