A recent study of citations to state supreme court opinions reveals that the California Supreme Court is most often followed by sister state supreme court.  The New York Times article describing the study includes the following:

In the 65 years ending in 2005, more than 24,000 state high court cases have been followed at least once. California leads with 1,260 decisions. Washington is next, with 942, and Colorado is third, with 848. New York comes in 10th and is only about half as influential as California, with 627 followed cases.

The study, published in the UC Davis Law Review is available here.

As a Supreme Court for the UK approaches, appellate judging is in the news. From The Times:

How many law lords does it take to decide a case? Normally, the answer is five. But last week and this, nine members of the Appellate Committee of the House of Lords are hearing two important cases. When the new Supreme Court opens its doors in October 2009, seven or nine justices should hear every case.

There are 12 law lords, if you count (and no one has done so for a long time) Lord Saville of Newdigate, who has spent the past ten years out of the office chairing the inquiry into the 1972 Bloody Sunday shootings in Northern Ireland and who is unlikely ever to return to judicial work even when (if ?) he finishes his report. But the remaining 11 law lords never squeeze around the same table to hear appeals. Almost all appeals are heard by five law lords. Exceptionally, nine of them listened to argument last week in a case brought by the President of the republic of Equatorial Guinea against defendants who he alleges conspired in England and elsewhere to overthrow the Government and seize power by means of a coup which, in the event, failed. And nine judges are this week hearing a case brought against the Prime Minister by two mothers whose sons were servicemen killed on duty in Iraq and who contend that there should be an inquiry into whether the invasion was in breach of international law.