How can I instantiate HTMLUnitDriver?

The HTMLUnitDriver can be instantiated as below:

WebDriver driver = new HtmlUnitDriver(); // Instantiate the class - org.openqa.selenium.htmlunit.HtmlUnitDriver

Sample code:

package tests;

import org.openqa.selenium.WebDriver;
import org.openqa.selenium.htmlunit.HtmlUnitDriver;

public class HTMLUnitDriverSample {
	public static void main(String[] args) {
		// Instantiate the HTMLUnitDriver
		WebDriver driver = new HtmlUnitDriver();

		// Visit the Selenium-WebDriver FAQ site
		driver.get("http://seleniumwebdriverfaq.tumblr.com/");

		// Print the title of the page - It should print"Selenium-WebDriver FAQ's"
		System.out.println("Title of the page is: " + driver.getTitle());

	}
}

What are the different implementations of WebDriver available?

Below are the WebDriver implementations available as off now:

1. HtmlUnitDriver
2. FirefoxDriver
3. InternetExplorerDriver
4. ChromeDriver
5. OperaDriver

6. AdroidDriver
7. IPhoneDriver

You can find out more information about each of these by following the links.

From where can I download set of Selenium tools?

Link below is where you can find the latest releases of all the Selenium components:

http://seleniumhq.org/download/