Google Web Directory of Programming Languages

HTDP

How to Design Programs offers a complete text of An Introduction to Computing and Programming, published by MIT Press.

The Language List

This web site is good for not only learning about older languanges but those that are current today. It does not claim to be a scholarly work and its success depends on the contributions of internet users, but it is quite comprehensive considering its listing of 2,500 computer languages.

Programmers Heaven

Java

Introduction to Computer Science Using Java

The website reviews the building blocks of computer science using Java in a general manner and offers a quiz at the end of each of the 87 chapters organized into 13 parts.

An Introduction to Programming in Java

This website contains nine basic sections of Java for the initial computer programming course. It supplements the recent publication of a textbook but can be used by itself and doesn't assume previous experience with computer programming.

Introduction to Programming Using Java

The Fifth Edition of Introduction to Programming Using Java, a free web-based resource that uses Java. The entire text is searchable and can be downloaded.

Javanotes 5.1 

This link presents the fifth edition of Introduction to Programming Using Java, which is a free, on-line textbook on introductory programming in Java. All content is searchable.   

Java Tutorials

A number of tutorials by Richard G. Baldwin to help learn Java.