The University of California system has proposed asking incoming freshmen to identify their sexual orientation. For now, they are only considering asking incoming students, but this is something that admissions offices at other colleges are beginning to explore.
Elmhurst College began to ask applicants about their sexual orientation last year. Elmhurst is affiliated with the United Church of Christ, which endorsed gay marriage in 2005. They even have some scholarships available for students who self-identify as gay in order to foster a more diverse campus community.
Asking students to report their sexual orientation on an admissions application or prior to enrollment serves a dual purpose. It is important for practical reasons so that colleges know what types of resources and support services they will need to provide for the incoming students. It also demonstrates that colleges recognize the value of a diverse student population, not just in terms of ethnicity and geography, but sexual orientation, as well.
For more details, you can read the full story at The Choice, a New York Times blog about college admissions.