Apress has decided to make some of their back catalog available as free downloadable e-books. [Via]{style="FONT-STYLE: italic"} [Eric Gunnerson's C# Compendium]
Andrew Troelsen’s “COM and .NET Interoperability” is the cream of the crop. Other texts are “Programming VB.NET: A Guide for Experienced Programmers,” by Cornell and Morrison; “Writing Perl Modules for CPAN,” by Sam Tregar; “Dissecting A C# Application: Inside SharpDevelop;” and “A Programmer’s Introduction to PHP 4.0”