There are several free, downloadable e-books at Apress here including
- Programming VB .NET: A Guide For Experienced Programmers
- COM and .NET Interoperability
- Google, Amazon, and Beyond: Creating and Consuming Web Services
- Dissecting a C# Application: Inside SharpDevelop
The last one is of particular interest. It describes the design, development and refactoring of SharpDevelop, an open-source alternative to the Visual Studio IDE.