Opera 7 is a substantial upgrade, with code rewritten from the rendering engine
and up, resulting in the fastest, smallest, most full-featured desktop browser
ever released.

-New rendering engine
Opera's new rendering engine supports W3C's DOM (Document Object Model) level 2,
non-standard dynamic HTML (DHTML), CSS1 and CSS2, ECMAScript, and has improved
HTML 4.01 support, as well as complete support for WML 1.3 and 2.0. It is
faster, smaller and can dynamically change documents through DOM.

-M2 -- new e-mail client
Opera's new e-mail client, M2, automatically categorizes and sorts e-mail
messages by contact and has an integrated spam filter. Innovative features such
as QuickReply and QuickFind lets users answer or find e-mails at unrivalled
speed. M2 supports POP3, IMAP, ESMTP, and threaded display of mailing lists.
In addition, M2 supports news servers with password authentication.

This is still a very early development version!

WWW: http://www.opera.com/