With the 3rd developer release of Mac OS X Lion being released a few days ago, there have been a few videos showing off some of the new features.
The boot/login screen of Lion has been updated, offering a cross-fade upon login.
To recap, here's a brief overview of Mac OS X Lion (including features found in previous developer releases)
This shows how Apple's "Reading List" works:
And here's how the new Safari download manager looks: