I've been focusing on JavaScript recently, so I missed this when it first came out:
Closures for Java. I think it is interesting that the motivation for finally doing this is to facilitate APIs for concurrency.
Sun will not be using any of the existing closures proposals as a starting point, but their initial ideas are perhaps closest to the FCM (first-class methods) proposal.
There are further details here including the ominous admission by Sun that they don't feel they can get any JSRs (for closures, Project Coin, or Java 7) approved by the JCP until they resolve their dispute with Apache. In the meantime, development of closures and the Coin extensions is happening outside of the JCP in the OpenJDK.
In related news, the schedule for OpenJDK7 has slipped and a final release is now due in September 2010. Note that this is the schedule for the JDK7, not for Java 7.
