The BBC's North America editor, Justin Webb, says the get-together in Unity is rich in political symbolism.
As well as the name, it is also the town whose Democrats were evenly split - 107 voted for Obama, 107 for Clinton.
Mr Obama and Mrs Clinton greeted each other with a kiss and a handshake when they caught the flight to New Hampshire on Friday. They also sat next to each other on the plane, the Associated Press reported.
Prior to Thursday's dinner, the two had not met in person since two days after the last primaries.
Latest opinion polls suggest that while Mr Obama has made headway in winning over Mrs Clinton's supporters since she withdrew from the nomination race, one in five of them has indicated they will vote for the Republican candidate, John McCain.
Our correspondent adds that Thursday's fundraising dinner was important for both sides - the Clinton campaign needs an injection of cash to pay off $20m (£10m) debts, but Mr Obama needs the financial muscle of the Clinton money raisers.
Mrs Clinton's advisers have warned Mr Obama that her ability to campaign on his behalf will be limited if she has to spend the summer raising money to pay off her debts.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.