There are various samples available for how to host Python or Ruby running on the DLR, inside your own AppDomain.
Are you able to do this yet with VB? There have been mentions of this since the DLR was announced 18 months ago, but I can't find a code sample for it.
Maybe with the PDC VS10 CTP? If so, what assembly contains the appropriate subclassed ScriptRuntime for VBx?
If this is not yet possible, can any MSFT-ies give us an update on when we might see some bits?
There's no release of VB (or C#) that is hostable via the DLR hosting APIs. In general the DLR hosting APIs, and the possibility of getting more MS created languages to support them, are tenatively thought to be post-Dev10. So it won't happen anytime in the short term.
Officially, there's no supported dynamic languages until VS10 is released. At that time, VBx, which apparently will be built on top of the DLR, will be released, probably alongside version 2.0 of the DLR. (Version 1.0's release is immanent.)
You might find some useful stuff in the VS10 CTP, but keep in mind it's neither supported, nor will there be much for documentation at this time. If you're hell-bent on hosting VB in your app, on the DLR, you'll just have to wait a year and a bit.
Looks like the VBx project died. There has been no word from Microsoft in years.