I've just seen Scott Gu's post, Silverlight 2 Release Candidate has been released-however the client size libraries will not be available. The purpose of this release is so developers can test and verify that there applications run as expected when the final release is available. (i.e. so don't deploy applications built against Silverlight 2 RC yet!)
This release features 3 new controls, a password textbox (woah), a combo box and a progress bar.