Nineteen countries allow gays and lesbians who are citizens to sponsor their non-citizen partners for legal residency. The US isn't one of them.
Some of these countries -- such as Belgium -- also recognize gay marriage; others, like Brazil, have not changed other laws but still allow gays to sponsor their partners for immigration purposes.
The US is currently looking to overhaul its immigration laws, but granting immigration rights to gay and lesbian couples isn't even on the agenda -- not a huge surprise in a country obsessed with "defense of marriage" laws, but depressing nonetheless.
This analysis is part of a longer report from Human Rights Watch called Family, Unvalued Discrimination, Denial, and the Fate of Binational Same-Sex Couples under U.S. Law, which can be read on the Web or ordered in book form.
Women's eNews has a report on how this issue particularly effects lesbian couples in today's issue. The Love Exiles Foundation provides general resources on the subject.
The nineteen countries that allow gays to sponsor their partners for immigration are: Australia, Belgium, Brazil, Canada, Denmark, Finland, France, Germany, Iceland, Israel, the Netherlands, New Zealand, Norway, Portugal, South Africa, Spain, Sweden, Switzerland, and the United Kingdom. Details of what each country allows are available here.