There are several areas which need to be addressed to get equality and equal treatment under the law.
DOMA, which denies gays the basic human right to the civil contract of marriage. Gay Marriage, recognized at the federal level, is perhaps the single most important one because it is so fundamental to ALL areas. The Supreme Court of the United States has already said that marriage is a fundamental right. Gays need access to that fundamental right.
DADT -- Don't Ask, Don't Tell, don't pursue -- which has been used to kick gays out of the military. For some reason the only part that is enforced is "don't tell". Kicking people out of the military for breaking the "don't ask" and "don't pursue" parts would be something Obama could do NOW which would send the right message -- and would suddenly get EVERYONE focused on getting DADT repealed.
Hate crime legislation. This is really legislating against the crime of domestic terrorism. Right now criminals are using the fact that they engaged in a hate crime to get REDUCED penalties by appealing to the bigotry of judges and jurors. The "gay panic" defense needs to be eliminated.
ALL of these need to be corrected at the federal level. These are basic, fundamental civil rights issues, and should not be left to individual states, any more than slavery should be left to individual states.