The site programmingebooks has an interesting collection of free available e-books about programming languages. The list itself is a little bit chaotic but it contains many programming languages, like HTML, PHP, Perl, Java and C++.
You find introductions to the languages as well as topics that are best suitable for advanced users. If you are currently learning a programming language or always had the desire to learn one but never wanted to pay lots of money for books this site is for you.
[tags]html, php, perl, java, c++, tutorials, book, ebook, e-book, help, introduction, programming[/tags]

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