Bill Clinton
- Bill and Hillary sought and successfully ended the racial overtones with adoptions, white adopt blacks and vice versa

and

Gerald Ford
- Operation Babylift
- Designated a national week for Adoption Awarness

I know some say that Obama was adopted by his step father in Indonesia. But, I am unaware of any documentation that is why I didn`t include it. He always refers to his father as the man from Kenya so I don`t know what to think!

Either way they were all adopted by their step fathers.
References :

Ronald Reagan – adopted Michael Reagan with 1st wife Jane Wyman

Andrew Jackson – Andrew Jackson Jr, a twin & the nephew of AJ’s wife. They also adopted son, Lincoya, a Creek Indian. The Jackson’s were guardians to 8 other children, orphaned relatives of his wife & of a family friend.

James Polk – and wife Sarah had no children but were guardians to Polk’s nephews.

James Buchanan – never married, guardian to two nieces

Grover Cleveland – birth father, arranged for his illegitimate son’s adoption by a wealthy NY couple

James Madison – step dad to Dolley Madison’s son

George Washington – step dad to Martha’s son & daughter

http://www.upstairsatthewhitehouse.com/presidents_children.php
http://ouradopt.com/adoption-blog/sep-2008/adoptionmaharishi/dear-adoption-maharishi-which-us-presidents-touched-adoptio

More info:
http://www.adopting.org/adoptions/u.s.-presidents-and-personal-connections-to-adoption-and-kinship-care.html

"The concept of adoption was not legally recognized in the United States until the 1850’s, with the inception of the first adoption statutes. While transfers of children to substitute parents had occurred informally since American colonial times, adoption statutes legitimized the informal adoptive arrangements which previously existed. During the early years of American society, no formal procedures existed for recording births or name changes. This facilitated an informal ability to have adoptive arrangements. Very often these informal placements were economically motivated. Farm families had great need for child labor. The advent of industrialization in the US resulted in massive immigration to major cites where families often were unable to support or care for their children. Informal transfers of these children to other families, by either the indigent parents or the charitable institutions where parents sometimes left their children, promoted these types of placements. This situation provided the impetus for the orphan trains between 1854 and 1929."

ETA: As mentioned, Bill Clinton was adopted by his step father. The difference between his adoption & most others is that Bill knows his history. Same with Gerald Ford. Most adoption records are sealed.

The Clintons did a lot while in office to support adoption by passing The Adoption & Safe Families Act of 1997, which removed barriers to adoption & increased adoption from foster care.
http://www.ncsl.org/programs/CYF/asfaslr.htm
http://www.hhs.gov/news/press/1999pres/990924b.html
http://edition.cnn.com/2000/ALLPOLITICS/stories/03/17/hillary.adopt/index.html
http://www.researchetcinc.com/historyofadoption.html

As always…there are two sides to every story…
"With the implementation of the Adoption and Safe Families Act, President Clinton tried to make himself look like a humanitarian who is responsible for saving the abused and neglected children. The drive of this initiative is to offer cash "bonuses" to states for every child they have adopted out of foster care, with the goal of doubling their adoptions by 2002, and sustaining that for each subsequent year. They actually call them "adoption incentive bonuses," to promote the adoption of children.

Everybody makes money. If anyone really believes that these people are doing this out of the goodness of their hearts, then I’ve got some bad news for you. The fact that this program is run by HHS, ordered from the very top, explains why the citizens who are victims of DSS get no response from their legislators. It explains why no one in the Administration cares about the abuse and fatalities of children in the "care" of DSS, and no one wants to hear about the broken arms, verbal abuse, or rapes. They are just business casualties. It explains why the legislators I’ve talked to for the past three years look at me with pity. Because I’m preaching to the already damned."
http://www.massnews.com/past_issues/2000/5_May/mayds4.htm
References :
BSE adoptee happily reunited in 1983

"Gerald Rudolph Ford, the 38th President of the United States, was born Leslie Lynch King, Jr., the son of Leslie Lynch King and Dorothy Ayer Gardner King, on July 14, 1913, in Omaha, Nebraska. His parents separated two weeks after his birth and his mother took him to Grand Rapids, Michigan to live with her parents. On February 1, 1916, approximately two years after her divorce was final, Dorothy King married Gerald R. Ford, a Grand Rapids paint salesman. The Fords began calling her son Gerald R. Ford, Jr., although his name was not legally changed until December 3, 1935. He had known since he was thirteen years old that Gerald Ford, Sr., was not his biological father, but it was not until 1930 when Leslie King made an unexpected stop in Grand Rapids that he had a chance meeting with this biological father. The future president grew up in a close-knit family which included three younger half-brothers, Thomas, Richard, and James. "
References :
http://www.fordlibrarymuseum.gov/grf/fordbiop.asp

Bill Clinton was born William Jefferson Blythe III in Hope, Arkansas. His father, William Jefferson Blythe, Jr., was a traveling salesman who died in an automobile accident three months before Bill was born. Following his birth, in order to study nursing, his mother Virginia, traveled to New Orleans, leaving Bill in Hope with grandparents Eldridge and Edith Cassidy, who owned and operated a small grocery store. At a time when the Southern United States were racially segregated, Bill’s grandparents sold goods on credit to people of all racial groups. In 1950, Bill’s mother returned from nursing school and shortly thereafter married Roger Clinton.

Although he assumed use of his stepfather’s surname, it was not until he turned fourteen that he formally adopted the surname Clinton, partially as a gesture toward his stepfather. Clinton says he remembers his stepfather as a gambler and an alcoholic who regularly abused his mother and, at times, his half-brother, Roger, Jr.
References :
Wikipedia

There were a few who were legal guardians, and a few ap’s, too.
http://www.heptune.com/preslist.html
References :

His dad’s name was William Jefferson Blythe III..Google it plenty of info
References :