Diigo (http://www.diigo.com/) is an awesome tool for bookmarking, but it goes beyond that! That is like saying a Lamborghini is just transportation. (If you have ridden in one of these things... I need to get to know you!)
This is a tool you should be using personally as well as with your students. It allows you to bookmark websites, as well as highlight content on that site. It's a cloud based organization system. They have great browser add-ins that add all of the functionality, as well as an iPad app (http://goo.gl/XCNz3). (Make sure you try the Diigo Browser http://goo.gl/iOqAB, it is one of the best browsers for the iPad. Formally it was the iChromy browser for the iPad.) You can even download the content for off-line browsing.
Many services are free, and they offer some premium features for a low cost. Check it out... and add the Google Chrome extension here: http://goo.gl/RulSI (Not using the Google Chrome web browser??? You should be!)
With the large number of Google apps and features being added constantly, it's hard to keep up as an educator. Here are just a few new features that you may not know exist, but could benefit your classes:
Comment only access in Google Docs. http://goo.gl/8R80j you can now share a worksheet, book review, or any Google Doc with students and allow them to freely add comments, but not change the content.
Page Level Access in Google Sites. http://goo.gl/KthNR You can now set permissions on individual pages in Google sites. This allows you to turn access on or off for specific individuals. You can share on your website that only a specific class or group of students can access.
Offline access for mail, calendar and docs: I have used Google Apps for over a year now, and have not really felt cheated by not having this option availbe to me, but it's a nice option to have avaialbe especially if you are headed out on a vacation and do not have access to the internet. It's also a nice option to have available if you are using a Chomebook. http://www.google.com/chromebook/ (I love these things.) Make sure you are using the Chrome Web browser (Shame on you if you are not.).
Scripting for Google Apps: OK, this takes a little bit of reading and tech-savy use, but if you manage it, the power is unbelievable. Self-grading quizzes, forms that email you, and more. Read more about this at my March 2011 blog entry.
Forms: I am amazed at how easy forms are to create and use with Google Apps. You can link that form right to your Google website to create a powerful online tool for registrations, surveys, quizzes and more. Combine that with the spreadsheet features of scripting and conditional formatting and you are in control! (For Example: Conditional formatting in a spreadsheet will turn a spreadsheet cell a certain color if a condition is met.)
Adblock plus is a really nice Google Chrome extension that a friend of mine just turned me on to. (Search the Chrome web store for this extension, or click here: http://adblockplus.org/en/ ) This add-on helps block a lot of the adds that are displayed on many of the sites. Does it catch all of them.. no, but it's a great start. I will say, I do not necessarily hate all ads, after all they help keep many sites free on the internet, but many adds, including flashing ones, or ones with skimpily-clad people selling weight loss supplements are really a pain. I give this add-on five stars... give it a try. Thanks to my friend, @joegehr for tweeting about this one!