Boilerplate sites are pre-designed templates that provide a starting point for web development projects. They often include basic HTML, CSS, and JavaScript files to help streamline the development process. Some of the best boilerplate sites include HTML5 Boilerplate, Bootstrap, and Foundation. HTML5 Boilerplate is known for its high-performance and robust features that help developers create fast and adaptable web apps or sites. Bootstrap is a popular framework that provides a collection of reusable code components, grid systems, and JavaScript plugins, making it easy to design responsive websites. Foundation is another advanced framework that offers a variety of responsive front-end tools to help developers build beautiful and functional web projects quickly.