I've posted a new article on Code Project. It is titled Compiling Multiple Projects Without a Solution. The article shows how to compile a multi-project application without using solution files (yes, it includes source code).
The code creates a MSBuild project file that will allow MSBuild to compile a list of VB.Net or C# projects in the correct order. The list can be loaded based on a root directory that contains .vbproj and/or .csproj files or a text file that can contain a combination of directories, project files, and/or other text files.