Google's new Toolbar 5 beta for Internet Explorer has a couple of very nice features including the ability to save your customised Toolbar settings via your Google account so you can access them from any computer. Google Notebook is now completely integrated - so you don't need to download a plug-in to be able to clip items from websites and save them with comments in your notebook. When you mouse over the clipping in your notebook, your comments appear like a tooltip.
You can also add gadgets to your toolbar to be able to view content from websites (such as YouTube).
The Google Operating System had a nice writeup of the new features, along with screenshots. You can download the toolbar here (and watch the Google video guide to the new features) or check out Google's guide to the new toolbar and features here.
Google Toolbar 5 for IE [Google Operating System]