Flock is a browser based on Firefox, and adding many social related features.

Opera is a fast and fuller-featured web browser.

Google Chrome is the browser launched by Google in September 2009. Based on Webkit for the DOM rendering engine completed with a brand new Javascript engine build by Google, Google Chrome has been build from scratch to optimize performance of rendering and use, Web 2.0 apps included. The source code of Google Chrome is code named Chromium, and accessible at http://code.google.com/chromium/ .

Ext GWT is a Java library for building rich internet applications with the Google Web Toolkit (GWT)

Clearspace is enterprise collaboration software built from the ground up for teams, companies, and communities looking for an easy and productive way to work with each other -- without time or location limitations. Eliminate redundant conversations, meetings, emails, and ideas by opening doors to new co-workers, partners, and customers.

The goal here is to do for email (starting with your personal mailbox)
what Google did for the web... The Google principle: It doesn't matter
where information is because I can get to it with a keystroke.
So what is Zoë? Think about it as a sort of librarian, tirelessly,
continuously, processing, slicing, indexing, organizing, your messages.
The end result is this intertwingled web of information. Messages put in
context. Your very own knowledge base accessible at your fingertip. No
more "attending to" your messages. The messages organization is done
automatically for you so as to not have the need to "manage" your email.
Because once information is available at a keystroke, it doesn't matter
in which folder you happened to file it two years ago. There is no
folder. The information is always there. Accessible when you need it. In
context.

Firefox is a fast, secure and fully customizable web browser.