I have been using del.icio.us for a couple of years now and grown used to web bookmarks that are easily accessible from whichever computer I'm using. Check out this blog (while you are there take some time to explore it - there are lots of useful tips on studying, learning and time management) on the advantages of del.icio.us, and then check out del.icio.us itself!
Visual dictionaries provide illustrations of words and concepts. Do you want to know what mesocarp* is and what is looks like? Use a visual dictionary. Merriam Webster has a glitzy one. Another Visual Dictionary (copyright by Bernard Dery, but no other information about the hosts of this site except that they are partnered with Wikipedia) has a simpler, but relatively deep dictionary. And then there's the quirkier, artier, visually satisfying Visual Dictionary which is a "collection of words in the real world. Photographs of signage, graffiti, advertising, tattoos, you name it." You couldn't find mesocarp in this dictionary, but you'd find a great illustration of "teenage"
Writer's Block and DarkCopy
Most writers, at some point, have a hard time putting words on a page. When we face that moment, distractions can further interfere with the writing process. DarkCopy has created an online 'distraction free' site where writers can enter text (which is saved automatically) without worrying about format, word count and all those other niggling details that can sometimes derail us. You can even make the writing box full-screen to further that writing immersion.
* it's the pulp of a fruit