Opera
Features
In addition to being extremely lightweight and quick Opera has a built-in BitTorrent client, and Email client.
Opera was the very first browser to support tabbed-browsing, and it has continued to innovate ever since, with features such as mouse gestures, voice control, custom skins, and "speed dial" which lets you access your favourite sites in seconds.
Even if you don't want to use the fancy features Opera still has a lot to offer. It is a rock solid application that takes up very few system resources.


