Diigo allows you to highlight and annotate directly onto webpages and PDF's, as well as bookmark and organize your annotated pages for easy retrieval later.
If you find that you're often printing articles or PDF's from the internet, Diigo may be particularly useful to you: rather than accumulating a lot of paper and having to organize and annotate them by hand, Diigo allows you to annotate, organize, and save all your articles and webpages in one location, so that you don't lose them.
This guide aims to cover only the basics of Diigo. For a more advanced look at using Diigo, feel free to visit Diigo's help page, at: http://help.diigo.com/
To download Diigo, go to https://www.diigo.com, and follow the instructions provided there.
Note that Diigo is not a stand alone piece of software in the same way as Zotero; instead, you create a free profile with Diigo and compile your library of annotated articles and PDF's on their platform.
To get the most of Diigo, be sure that the Diigo browser plugin is installed as well. Above is the plugin download screen for Chrome, but Diigo is also supported for Firefox.
With the browser plugin installed, navigate to your desired page. You can then annotate the page one of two ways.
First, clicking on the plugin at the top of your browser will display several options, including "Save Bookmark," which saves that page to your Diigo account, "Read and Annotate," which allows you to highlight and write notes directly onto the webpage, and the "Share feature," which allows you to email or link your annotated document, so that you can send it to others.
The second way to annotate your desired webpage is by by clicking and dragging over the text. This will open three options automatically: highlight, which allows you to highlight the selected text; annotate, which allows you to post notes about the selected text; and search in Google, which will search for the selected text in Google. To view all your annotations on a single webpage, select "Open Outline Sidebar" from the plugin drop down menu; this will display all your highlighting and notes in a column on the right hand side of your browser window.
If you would like to share the webpage with your annotations included on it, click on the plugin icon, and click the "share" icon from the drop down menu. From there, you can choose to share your annotated webpage via Twitter, Facebook, Google+, email, or link.
You can access all of the webpages you have annotated by logging into Diigo, and clicking "My Library." You can also add tags to your annotated webpages to more easily retrieve them later.