Apple will introduce new versions of iOS and OS X at its annual developer's conference.
Safari 4 Tips, Tricks and Special Effects
CSS Animation: Falling Leaves, Bouncing Box, Pulse
3D with Canvas: JS Cloth, Miku, Touch (via Kawanet and Ajaxian)
Presentations: Sample slideshow (use right/left arrows to advance)
Finally, those who are still trying to get used to the new Safari 4 changes might want to follow these tips:
Safari 4 Hidden Preferences - how to move the tabs back to the bottom, restore the blue loading bar, turn off URL autocompletion, Google Suggest and more. (Original site is down - content copied here.)
1Password - How to get 1Password to work in Safari 4