There is a public subversion repository for the ArcDeveloper hosted at Assembla.com. The repository can be accessed at:
http://svn2.assembla.com/svn/arcdeveloper
Anyone with a Subversion client can browse the source tree and download the code. If you want commit access, you'll need to set up a free account at Assembla, and contact Dave Bouwman (use the Contact link on the left) and I'll send you an invite to join the project.
EditREST API for ArcGIS Server 9.2
This project is focused on creating a simple REST API for ArcGIS Server 9.2. At this point it return GeoJSON by feature, or by query. Design wise, it uses a provider model, so it's pretty simple to extend to other back end services. After the May release of SQL 2008, (apparently they Lat/Long, Y,X thing will be fixed), expect to see some progress on a read/write provider.
At this point it's very basic, but it's got enough in there to be useful today.
The source code includes a simple demo, which can also be seen here:
http://65.101.234.201/rest/If you want to see the GeoJSON - you can open this Url in a text editor:
http://65.101.234.201/rest/rest.svc/testservice/flyway/1?g=true
Edit
This project is focused on building an extensible tile server using .NET. The inital release is focused on Virtual Earth, but it will be expanded to handle WMS-C and Tile Map Service requests. It has adaptive caching built in, and can support multiple map services. The initial release is focused on the base architecture and an ArcGIS Tile Provider that uses the ArcGIS Server SOAP API. The project is designed around a plug-in framework which will allow any map engine to be utilized.
This project also uses the Castle Windsor Inversion of Control Container to handle dependency injection and configuration.
EditVisual Studio Tempalates
This is a set of simple Visual Studio templates that can be used when writing code for ArcDeveloper.net. The templates themselves are easily modified and can be used by anyone as a starting point. All you need to change is the header and licensing in the actual files, and then use the MSBuild task to re-package them all up.