Claros, which is a passionate team in creating open source software, has a beautiful software named Claros inTouch.
Clasor InTouch is an ajax communication suite with key features such as webmail, address book, post-it notes, calendar (in progress), webdisk (in progress), built-in instant messenger and RSS reader. It is the first open source web application which features built in spam protection and instant messaging capabilities together with web 2.0 technologies.

It is built with Java, utilizes JSP/Servlets with the well known J2EE technologies & uses MySQL database.
Claros inTouch is more than a free webmail software with a slick interface & usability.
It is offered under GNU which makes this communication suite software totally free.
Requirements: Tomcat For JSP & MySQL
Convert HTML To ASP, PHP Or JSP? The title might seem fancier than the reality.
Response.Right is a web based tool which converts HTML into a variable (which is, probably, one of the top 10 hated tasks of a web developer).
This tool is very useful, for example, when creating a html mail that will be sent via a dynamic scripting language or converting large amounts of html that will be used inside these dynamic languages.

Supported programming languages:
- ASP - Javascript
- ASP - VBScript
- JSP
- PHP
Accessify.com offers some other free web based tools like Insta-Select (XHTML-compliant select list generator), Acrobot (converts all your acronyms/abbreviations using the <acronym> and <abbr> tag) & more.
Requirements: No Requirements