Top 100 open source Web Development Tools and applications

Web development tools which are open source have great benefits, including free to use and modify code. Thus lately I have been rigorously mapping all the free and open source apps & tools that are useful and easy to use for web developers. Many I have used or come across during my routines.  So presented below you can find the 100 Best tools and applications oriented towards the efficient web developer..
Note I will possibly have missed some notable web development tools in this list of open source apps but feel free to comment on any tools or applications you would like added to this list..

Code Editors

1. Aptana

The Aptana IDE is a free, open-source, cross-platform, JavaScript-focused development environment for building Ajax applications. It features code assist on JavaScript, HTML, and CSS languages, FTP/SFTP support and a JavaScript debugger to troubleshoot your code.
Read more on Aptana

2. Eclipse

Eclipse is an open-source software framework written primarily in Java. In its default form it is a Java IDE, consisting of the Java Development Tools (JDT) and compiler (ECJ). Users can extend its capabilities by installing plug-ins written for the Eclipse software framework, such as development toolkits for other programming languages, and can write and contribute their own plug-in modules. Language packs are available for over a dozen languages. (Source Wikipedia)
Read more on Eclipse

3. jEdit

JAVA Interview Question

What is Collection API ?
The Collection API is a set of classes and interfaces that support operation on collections of objects. These classes and interfaces are more flexible, more powerful, and more regular than the vectors, arrays, and hashtables if effectively replaces.
Example of classes: HashSet, HashMap, ArrayList, LinkedList, TreeSet and TreeMap.
Example of interfaces: Collection, Set, List and Map.
Is Iterator a Class or Interface? What is its use?
Answer: Iterator is an interface which is used to step through the elements of a Collection.
What is similarities/difference between an Abstract class and Interface?
Differences are as follows:
Interfaces provide a form of multiple inheritance. A class can extend only one other class. Interfaces are limited to public methods and constants with no implementation. Abstract classes can have a partial implementation, protected parts, static methods, etc.
A Class may implement several interfaces. But in case of abstract class, a class may extend only one abstract class. Interfaces are slow as it requires extra indirection to to find corresponding method in in the actual class. Abstract classes are fast.
Similarities:

Neither Abstract classes or Interface can be instantiated.
Java Interview Questions - How to define an Abstract class?
A class containing abstract method is called Abstract class. An Abstract class can't be instantiated.
Example of Abstract class:
abstract class testAbstractClass {
protected String myString;
public String getMyString() {
return myString;
}
public abstract string anyAbstractFunction();
}