We've been impressed with Diigo, a content sharing and bookmarking tool. It pulls double duty as a way to clip things from the Web, as well as share them with others. What makes the service really interesting is that you can use it to grab entire Web pages, and make annotations right on top of the content. Then you can share it with others, or view it even when the source site is no longer there, like a personal archive.
The service has a plug-in that lets you clip and save text from Web pages, or just page URLs themselves. You can categorize and tag your findings for later, and keep your stuff private, shared with friends, or make it public. A nice browser sidebar shows you lots of useful and focused information, including your own latest bookmarks, those from your Diigo friends, and most cleverly, the Diigo users who have also saved information from the page you're visiting, as well as the site itself.
We recommend Diigo, especially with the plug-in. It's a complex tool, but if you take the time to surmount the learning curve, it can make you a smarter, more productive Web user.