There are so many sources of technical information on Virtual Earth that I am never sure that I have found them all or am using the best ones. Therefore I found Soul Solutions post here really useful.
So here is their recommended list:
This is a simple list of the various resources available for your development needs.
Official Microsoft:
- Virtual Earth API on MSDN
- Virtual Earth Interactive SDK
- Microsoft MapPoint Web Service API on MSDN
- VIRTUAL EARTH SERVICE API TERMS OF USE
- Geographic Coverage Details
- Streetside Technology Preview
- Windows Live Maps for Mobile
Community sites:
- ViaWindowsLive – Virtual Earth Section.
ViaVirtualEarth – Orginal community site, archive of older articles, forums and gallery items for VE1->5.
Community Projects:
WinForms Control – A must for anyone looking at using VE in a windows forms app.
Tools:
- Intellisence for Visual Studio 2008
- View the interactive Virtual Earth Quick Guide
- Virtual Earth Location Finder
- Spatial Extensions for SQL Server 2005
- General Polygon Clipper library
- Determining if a point lies on the interior of a polygon
Blogs:
- All blogs Aggregated
- Virtual Earth / Live Maps
- Heptazane’s Stump
- Virtual Earth, a developer blog
- Virtual Earth For Government
- Hannes’s Virtual Earth Blog
Virtual Earth 3D (spaces)
Virtual Earth 3D (msdn – 3d control code in c#)
Exams:
Update:
I also love this quick guide that makes a great starting point:
http://www.viawindowslive.com/Resources/VirtualEarth/VirtualEarthQuickGuide.aspx

True! Soul Solutions has some good resources on their site. I found them on Via VirtualEarth – lots of the sites listed there are down.