Thunderbird is a total redesign of the Mozilla mail component to produce a cross-platform, stand-alone mail application using the XUL user interface language. It has many new features, among them the ability to customize your toolbars the way you want them. a new look and feel with a large number of downloadable themes which alter the appearance of the client, and the ability to add UI extensions.
Roundcube Webmail is a browser-based, multilingual IMAP client with an application-like user interface. It provides the full functionality you expect from an email client, including MIME support, address book, and folder manipulation. High extensibility is granted by the plugin API and the user interface is fully skinnable using XHTML and CSS 2.
Joomla contact form builder extension is a complicated tool for making submission forms for your Joomla website. It permits you to specify parameters like colors and fonts. It can use a Google map when given an address or geographical coordinates (longitude and latitude), and the user can drag the marker to the required location.
WordPress FAQ is a cool plugin for creating your FAQ section . It has a lot of parameters to set, and it will allow you set your own theme from scratch. It has a user-friendly front-end and back-end interface, allowing you to set all parameters quickly and easily. FAQs have SEO-friendly URLs.