Sen. Patrick Leahy ( D-Vermont ) introduced the Uniting American Families Act ( S. 424 ) earlier this year; it has 18 co-sponsors. The bill would allow same sex couples the same immigration rights as married heterosexual couples. Passage of the bill is likely to be tied to overall immigration reform.
At the moment, same-sex partners of legal immigrants do not have the same rights to dependent status that heterosexual spouses get. This is true even if the couple is legally married in their home country. Often, the "dependent" partner must apply for a B-2 visitor visa at the consulate, to accompany his/her partner. This visa is discretionary, and consulates could refuse to issue it. In addition, B-2 status does not allow the dependent partner to work in the US. Many heterosexual dependent spouses have a status that doesn't allow them to work either, however.
As the New York Times reports:
Photo by http://www.flickr.com/photos/boscobridalexpos/Senator Leahy’s bill would add the term “permanent partner” to sections of current immigration law that refer to married couples, and would provide a legal definition of those terms.
“I just think it’s a matter of fairness,” he said Tuesday in an interview, noting that a number of American allies, including Canada, France and Germany, recognize same-sex couples in immigration law.