There are two separate cases, Windsor (on the constitutionality of the Defense of Marriage Act, or DOMA) and Perry (on California’s Proposition 8). Both cases are scheduled for oral argument on March 27.
The Court’s docket provides information on filings and developments in the two cases here and here. On Tuesday, former Solicitor General Paul Clement, who represents the Bipartisan Legal Advisory Group (BLAG) in its defense of DOMA, filed a brief on the merits (read it here). Also on Tuesday, the Petitioners in Perry filed their merits brief in defense of Proposition 8.
In addition to its extensive news and analysis, SCOTUSblog provides access to many of the briefs filed in these cases (here and here) in its Merits Cases section. There is no better place to stay current on news and developments related to these cases and others pending at the Supreme Court.