More and more tools with UML2 support are emerging. Currently, however, UML 1.x is still dominating the tools market. Some tools are listed on modelbased.net – UML tools.
Some arguments on NOT using UML2 and the (fierce) reaction of Andrew Watson (technical director at OMG) on that (scroll halfway the article for Andrew’s reaction) are worthwhile reading.
An older but thorough review on UML tools (not the UML2 ones) is available on the site of Mario Jeckle (http://www.jeckle.de/umltools.html) who died last year but whose site is kept alive.