The Rainbow World Fund, an all-volunteer LGBT international humanitarian service agency, has created a Japan earthquake fund.
Among the hardest hit cities is Sendai, Japan. In 1997, Mayor Ron Kirk signed a friendship agreement with that city. No word yet on whether Dallas will mount a separate relief effort for Sendai.
From the Rainbow Fund Japan relief page:

A 8.9 earthquake followed by a tsunami stuck northern Japan on March 11, 2011. Nearly 1,000 have died and thousands still remain unaccounted for. Thousands have been injured, hundreds of thousands are now homeless. Millions are without water, food and power. Several nuclear power plants were impacted, radiation has escaped and there is a threat of a meltdown. Many aftershocks above magnitude 6.0 have occurred.

At the request of our generous donors, RWF has set up a fund to help the Japanese people recover. RWF has many direct ties with Japan through our annual World Tree of Hope project which is a collaboration between RWF and members of the Japanese American community.

To make a donation, click here and specify “Japan.”
To make a donation by check, mail to Rainbow World Fund, P.O. Box 14480, San Francisco, CA 94114-2336.
Rainbow World Fund helps people who suffer from hunger, poverty, disease, oppression and war by raising awareness and funds to support relief efforts around the world. They bundle LGBT dollars “to change perceptions of the LGBT community by putting our truest humanitarian beliefs and values into action which demonstrates our compassion and caring for the world,” according to their website.
UPDATE:
JASDFW Establishes Relief Fund for Tsunami Victims
The Japan America Society of Dallas Fort Worth has launched an emergency relief fund that will be used to aid relief and recovery efforts in Sendai, Japan.   Sendai and Dallas have been International Friendship Cities since 1997.
Those wishing to contribute to the fund may do so by sending their contributions to Japan-America of Dallas /Fort Worth, 11615 Forest Central Drive, Suite 26, Dallas, Texas 75243.
“The fund was established in response to the many inquiries our organization has received from people wishing to help,” said Anna McFarland.
Money raised through the JASDFW fund will be sent to organizations involved directly with relief efforts in Sendai, which was one of the cities hardest hit by the disaster.
“We are just now realizing the depth of the destruction and loss of human life in Japan as a result of the 8.9 earthquake and tsunami that struck Japan on March 11,” said David Schnetzer, president of the JASDFW.
Reports now estimate the death toll may exceed tens of thousands.
As Friendship or Sister Cities, Dallas and Sendai have worked together to establish cross cultural understanding, educational and sports exchange programs and to promote business and economic relationships between the United States and Japan.
For more information about JASDFW’s Sendai Relief Fund or the city of Sendai, contact Anna McFarland, JASDFW Executive Director at 214-342-2022.