JumpKnowledge Annotator is a great tool for blogs that critique and comment on other sites. You can compare and contrast multiple news articles on the same subject (annotations can span multiple pages from the same or different site.) Make in-line corrections to a site and email it to the Web master. If you experience a problem or error with a Web-based application, you can email the page to technical support with your comments right next to the error.
You can share password-protected pages. For example, you can capture one page of your online bank statement and share it with a friend. This way, you don't have to give out your password and you are able to limit what your friend can see. Research studies, especially if you refer to online Web page which may disappear tomorrow.
Webware, Internet Explorer 6 and 7, Firefox 1.5 and 2