The name of Kwanzaa was derived from the Swahili phrase "matunda ya kwanza" which means "first-fruits."  It is based on the first harvest celebrations which take place throughout Africa.  This holiday season was developed by Dr. Maulana Ron Karenga and first celebrated in 1966.
Kwanzaa is celebrated from December 26 through January 1, for seven days. Each day of the celebration focuses on a principle which helps define the African cultural identity and promote a connection between all peoples of African heritage.  Collectively, these seven principles are called the Nguzo Saba.  Even though they are individually focused on during Kwanzaa, they are meant to be upheld throughout the year, and as a part of life.
The development of Kwanzaa in the late 60s is important not only because of the social unrest between American cultures at the time, but also because Americans of African descent had no culturally distinct holiday to celebrate.  Other American holidays focused either on the ancestry of other cultures, or were too commercial.  With Kwanzaa, African-Americans now had a holiday in which to focus on their own principles, and to bring their families together to relate the past and look to the future.
Today Kwanzaa is a way of life and is celebrated throughout the world.  It is an essentially positive holiday in which all people of African descent can recommit themselves to the Nguzo Saba, in order to better their lives and the world around them.
To read more about Kwanzaa:
Kwanzaa - Wikipedia

Kwanza Kids' Party Fun

MelaNet Kwanzaa Information Center
What is Kwanzaa?
Kujichagulia -- Self-determination, to determine ourselves rather than allowing others to define us.
Ujima -- Collective work and responsibility to our community brothers and sisters.
Ujamaa -- Cooperative economics, in which to build our own businesses and profit from them together.
The Nguzo Saba:
Umoja -- Unity in family, community, nation, and race.
Kuumba -- Creativity, in order to leave our community better and more beautiful than we found it.
Imani -- Faith, believing in our people, parents, teachers, leaders, and victory of our struggle.
Nia -- Purpose - developing community to restore traditional greatness.