Safari Books Online is a digital library providing on-demand subscription access to thousands of learning resources.
Safari 4 is Big Brother-ish in a good way: it keeps track of where you've been, and how often and how recently you've been there, and cleverly calculates a Top Sites list stripped of such distractions as sign-in pages and multiple pages from the same site.
The presentation of Top Sites can be deceiving: more than just eye candy, it provides a way to scan multiple, identifiable thumbnails in an instant—you'll wish you could view your bookmarks and history in the same way.