One thing our students do on a very regular basis is read on the web. Teachers at our school have spent time helping kids annotate printed text, and now there are some pretty cool tools to help kids annotate web-based text. If annotating is a strategy you use with students, the three free tools below are worth checking out.
SharedCopy is a free tool that you can use on the web to highlight and add sticky notes. You do need to create an account first if you want to save what you've annotated, but it is email-based, meaning that our students can create an account based on their school email (makes it easier for us to troubleshoot).
You can install the SharedCopy button onto the browser's toolbar (see your technology support person if you need help), and it currently works with Safari, Firefox, & Explorer. Clicking on that button will bring up a small window with various tools you can use to mark up a web page. What's great for students is that they can access their "stored" pages from anywhere and can email their teachers their work. Because SharedCopy basically takes a snapshot of the page, this is a great option for using with subscription databases.
Another good highlighter/sticky tool is AwesomeHighlighter. While this is only available as a toolbar button for Firefox, you can always go to the AW web page and paste in a URL for highlighting. One of the things AwesomeHighligher has going for it is the ability to color code. You can choose from 4 different highlighter colors, which is something that SharedCopy currently doesn't do (you can only use yellow). Like SharedCopy, you'll need an account if you want to save your highlighted pages, but this one is also email-based.
Finally, if you want your students to be working in groups, sharing web pages, and annotating those pages (in addition to highlighting), Diigo.com is well worth your time. It has a lot of features, so it takes a bit more front-end work than the aforementioned tools, but it also has a lot of potential. Not only can you highlight and share page annotations, but you can collect them in one place and have online discussions. Teachers can create an educator account (& student accounts via upload), but accounts are required (email-based).
So how does this relate to comprehension? When working with web-based reading, we can guide our students in not only highlighting but also adding sticky notes to explain their choices or adding sticky notes with questions that they have as readers. They can then share that with the world, if they want, and see what others have annotated. These 3 (free) tools can help our students learn how to work with electronic text in ways similar to printed text.