There's a very cool web site called The Burning Edge that I just ran across. It blogs developments in nightly builds of Mozilla Firefox. Even if you don't use nightly builds, it has a "bigger picture" page that describes new features that will be in the next release. I just got 0.8 and I'm already excited for 0.9! I'm especially excited about new feature 189888 which shows a warning dialog when closing a multi-tabbed browser window. Major improvement 231995 isn't too shabby either.