Sorry for the delayed reply!
We have not yet released Silverlight 3 builds of the controls. There are some subtle differences between SL 2 and 3 and we will need a few weeks to convert the controls to SL3 so that they will be tested and work as expected.
Still, most of the functionality should be unaffected when you use the SL2 builds in a SL3 application.
I created a simple example with comments that will hopefully get you started with DragDrop in SL3 in VisualBasic. I am sorry that we have not provided more examples in VB, we are planning to address this issue in a help update coming for the Q3 release.
I am attaching the sample project.
the Telerik team