This came through on an internal list today. The author, Asli Bilgin, warns that this is "BY NO MEANS a comprehensive list", so if you've got more, leave them in the comments here.

VSTO Resources

bits & bytes

• Get Microsoft Visual Studio 2005 Tools for the 2007 Microsoft Office System
• Visit the Visual Studio Tools for Office Forum
• Visit the VSTO Developer Center
• Get the OBA/VSTO Starter Kit v. 1.0
• Try the O2 OBA Challenge
• Visit OBA Central

Webcasts

• MSDN Webcast: Visual Studio Tools for Office Straight from the Experts: Ken Getz (Level 200)
• MSDN Webcast: Visual Studio Tools for Office Straight from the Experts: Robert Green (Level 200)
• MSDN Webcast: Visual Studio Tools for Office Straight from the Experts: Tim Huckaby (Level 200)
• MSDN Webcast: Visual Studio Tools for Office Straight from the Experts: Paul Ballard (Level 200)

Blogs

• The nicest man at MSFT (and he plays a mean guitar too): Mike Hernandez Blog
• Paul Stubbs – Senior Program Manager
• VSTO2 blog
• Best of VSTO blogs
• Brian Goldfarb, Group Product Manager – he can demo a fetching VSTO
• Chris Castillo's WebLog
• John Durant
• Tim Huckaby
• Ken Getz blog
• Kathleen McGrath
• Paul Ballard

Tech talks

• VSTO and security – Eric Lippert, VSTO team, senior software dev engineer
• Scope of VSTO Martin Sawicki, program manager VSTO
• Why a VSTO Runtime? Thomas “TQ” Quinn – Principal Architect & Christin Boyd – Customer Program Manager (she KNOWS things, just ask her)

demos

• Video Demo: VSTO and VBA Interop
• How Do I Videos
• VSTO demo Catherine Heller, Technical Evangelist – Windows Live
• Extend VBA with .NET Eric Schnepp, Principal Program Manager in the VSTO team

labs

• MSDN Virtual Lab: Building Custom Office Applications Using Microsoft Visual Studio Tools for Office Part 1 - Data Binding with Word Content Controls 
• MSDN Virtual Lab: Building Custom Office Applications Using Microsoft Visual Studio Tools for Office Part 2 - Create an Outlook Add-in with a Form Region
• MSDN Virtual Lab: Building Custom Office Applications Using Microsoft Visual Studio Tools for Office Part 3 - Build an Excel Add-in with Ribbon and Custom Task Pane Integration
• MSDN Virtual Lab: Building Custom Office Applications Using Microsoft Visual Studio Tools for Office Part 4 - Create a SharePoint Workflow