You can now view the webcast I gave this month talking about VSTO futures in particular the future releases of VSTO that can be used to do Office 2007 development.
I talk about VSTO 'Cypress' which is the next release of VSTO that will ship simultaneous with Office 2007 and will install on top of VSTO 2005. I also talk about VSTO 'Orcas' which will have more advanced features for targeting Office 2007.
I also do some basic demos of both products--not too advanced but it should give you a basic idea of how to program against the new Office 2007 application-level custom task panes and the Office 2007 ribbon.
Link to Webcast