The Supreme Court today
agreed to hear Hamdan v. Rumsfeld. This is a major case testing the extent of Executive power during wartime.
Specifically, the Court will consider the constitutionality of Bush's military tribunals trying so-called "enemy combatants". The Court had previously taken no action on whether to accept this case, but now that it has, the Hamdan case becomes one of the most important of the Court's docket this term.
Chief Justice Roberts, who had ruled on this case on the D.C. circuit, recused himself from the certiorari vote (i.e. the vote on whether the Court should accept the case). He will likely recuse himself from participating in this case at all, setting up the very real possibility of a 4-4 split on the Court (which would uphold the D.C. Circuit's pro-government position).
For further information, the D.C. Circuit's opinion can be found here. A helpful mini-summary of the case can be found here, and I would recommend reading this helpful analysis by Prof. Michael Dorf concerning what is at stake in this case.