Last night at the MOSSIG meeting I demo-ed a few VSTO Add-ins I've created recently showing how to expose business data in Word and how to save an email to SharePoint from a context menu in Outlook.
A few questions where about where to download VSTO etc., I came across this MS-page that actually has nice recap of all new stuff for developers.
The seperate VSTORuntime is here. I'll be bLogging a few code samples in the next few days.
Lots more info and updated documentation on the new Office Developer Centre. Be sure to check that out!