The OMG has released a new UML version (2.4.1). Most changes are related to the internal structure of the UML metamodel and do not affect you as a modeller!
For those who are interested in the UML metamodel, the OMG provides a machine readable format of UML 2.4.1, serialisation in XMI. This XMI documents may be
imported into Enterprise Architect and studied in your familiar toolset.
The XMI resources can be downloaded from here: http://www.omg.org/spec/UML/20110701/
The UML specification is available as PDF: http://www.omg.org/spec/UML/2.4.1/
If you are interested in the changes made in UML 2.4.1, download the non-normative version of the pdf, it includes change bars.