Mr Obama has announced that Illinois congressman and fellow Chicagoan Rahm Emanuel will head his White House staff, and said at his first news conference on Friday that he expects to make other announcements within weeks.
Here are some of the possible choices for key Cabinet positions.
Secretary of Defence - Defence Secretary Robert Gates was sworn in by outgoing President George W Bush on Dec 18, 2006. Mr Obama voted to confirm him. Mr Gates served as CIA director from 1991 until 1993.
- Mr Richard Danzig is a close adviser to Mr Obama. He served as Navy secretary under President Bill Clinton. He also served as Navy undersecretary from 1993 to 1997.
Treasury Secretary - Mr Lawrence Summers served as Treasury Secretary under Mr Clinton. The former president of Harvard University has been a top adviser to Mr Obama.
- Mr Timothy Geithner is president of the New York Federal Reserve Bank. He served as Treasury Undersecretary for international affairs during the Clinton administration.
Secretary of State - Senator John Kerry of Massachusetts was the Democratic candidate in the 2004 presidential election. A Vietnam War veteran, he was first elected to the US Senate in 1984.
- Mr Sam Nunn is a former senator from Georgia who chaired the Senate Armed Services Committee. Mr Nunn has long been viewed as a leading Democratic voice on foreign policy.
- Senator Chuck Hagel of Nebraska, an outspoken member of the Committee on Foreign Relations, has been a leading Republican critic of the Bush administration's Iraq invasion. He is retiring from the Senate, having served two terms.
Director of the Office of Management and Budget - Mr Peter Orszag has headed the nonpartisan Congressional Budget Office since January 2007. He previously served as an economic adviser to President Clinton.
US Trade Representative - Mr Dan Tarullo is a professor at Georgetown University law school. He is a specialist on trade and international economics. As a senior White House aide to Mr Clinton, he helped prepare for meetings of the Group of Seven industrialised economies.
Attorney-General - Mr Eric Holder served as deputy Attorney-General under Mr Clinton. He has been a senior legal advisor to Mr Obama's campaign and helped vet Mr Obama's vice-presidential candidates.
- Arizona Governor Janet Napolitano, first elected in 2002 and re-elected in 2006, is a former US Attorney. She has been called a pro-business centrist Democrat.
Agriculture Secretary - Mr Tom Vilsack is a former governor of Iowa, an agriculture state carried by Mr Obama. In 2006 he became the first Democrat to announce his candidacy for president. He quickly withdrew and later endorsed Senator Hillary Clinton. Mr Vilsack is an attorney who specialises in energy conservation, renewable energy and agribusiness development.
- Kansas Governor Kathleen Sebelius, re-elected to a second term in 2006, had been considered a potential running mate for Mr Obama.
- Mr Charles Stenholm, a former Democratic congressman from Texas, was a cotton producer before running for Congress. He followed agricultural issues closely until he lost his seat in the 2004 election. -- REUTERS