From the December sitting, four opinions are outstanding: three from important constitutional cases -- Ashcroft v. Raich (which was actually argued on November 29th, technically at the beginning of the "December" sitting), Granholm v. Heald, and Veneman v. Livestock Marketing -- as well as Miller-El v. Dretke (also important, but not technically a constitutional case). Of those four opinions, Justices Stevens, Kennedy, and Souter are likely writing at least one majority apiece, and Justice O'Connor almost certainly is not writing a majority.
Two of those three are most certainly in the liberal camp (and with what the rightwingers are saying about Kennedy, maybe he's now considered one of ours too). Now, I know nothing of Granholm, Veneman, and Miller-El, but Raich is something I have expressed thoughts on. For those of you who don't know, Raich is a Medical Marijuana case which deals with whether or not California's medical marijuana plan sufficiently implicates inter-state commerce such that it can be regulated (read: superceded) by the federal governments anti-drug statutory scheme. What makes this case particularly interesting is that it represents a conflux of liberal means to conservative ends. That is, if one accepts that there is a broad congressional power to regulate interstate commerce (as most liberals do), then one would be inclined to permit Washington's overriding of California's medical marijuana plan (a conservative outcome). Conversely, if one takes a narrow view of the ISC clause (as conservatives do), then Washington's efforts become more suspect and the marijuana plan might be saved (a liberal position). There might be some mighty fine hair-splitting in the opinions for this case.
Perhaps it is that difficulty which has caused the long delay in hearing from Raich (link: Randy Barnett, who represented Raich in the case).