Diigo  is simply one the coolest websites I've come across lately. It lets you highlight text on a webpage, just like you would in a book (not a library book of course, but you knew that) or notes, choosing yellow, pink, green or blue to suit your mood. You can also add a sticky note to the page to write comments on. Here's the really cool part, if you leave the webpage and come back, your hightlights and sticky notes are still there. If you close your web browser and reopen it to that webpage, your highlights and sticky notes are still there. If you log off your computer, log back on, and open your browser to that page, that's right, your hightlights and sticky notes are still there! Diigo also consolidates all your highlighed areas from different webpages in one place, your Diigo home page. You can always delete highlights and sticky notes whenever you want, or just log off Diigo and they will vanish until you log back on.
How do you get Diigo ? You simply download the diigo program to your computer, it's free and should only take a few seconds with a highspeed internet connection. You can create an account using your Google/Gmail or Yahoo email address, or you can create a Diigo account from scratch. Note: when it asks about emailing your friends, I would suggest skipping that or it will harvest all your email contacts.
"How helpful is it to bookmark a Web site if you need only one sentence from that 3,000-word article? Diigo is a free bookmarking service that lets you do what we wish Yahoo's Del.icio.us would: highlight text and comment on Web pages. Diigo caches each site so that you can search within text, not just the topic tags. And you won't have to leave the Del.icio.us community, since Diigo lets you save bookmarks simultaneously in both places." --CNET, Top 10 Research Tools