1. Easier downloads.
The new Download Manager tracks when you downloaded files and from where.2. An enhanced address bar.
The address bar is now more readable, and as you type in a URL or word, it searches both your history and your bookmark lists for matches.

3. A workable bookmark organizer.
The new Places Organizer vastly improves Firefox’s management of bookmark lists. For instance, you can immediately edit a bookmark’s name, location and tags rather than having to go into the Properties box.

4. Easier bookmarking.
Firefox 3 Beta 2 includes a number of useful bookmarking features. For example, you can quickly create a bookmark by double-clicking on the star in the address bar.

5. Better memory management.
The new version of Firefox appears to have a smaller memory footprint than its predecessor. In my quickie test, Firefox 3 Beta 2 used 2,500KB less memory than the 48,968KB that Firefox 2 used to perform the same functions.

Complete Article + Screenshots : Computerworld