Google Reader

What is it?  Google Reader is a Web-based aggregator, capable of reading Atom and RSS feeds online or offline.

Kristina Cummins writes a nice blog post on how you may use some of the functionality of Google Reader.
Link:  www.google.com/reader

Quizlet

Sick of spending hours look at old notes or handwriting flashcards for an exam that's coming up in (insert panic) three days?! Quizlet.com is your answer. You can type in your own flash card terms and definitions, look up previously used terms by subject, or if you already have a digitized list of terms and definitions, you can just copy and paste them right into Quizlet just by letting it now what's in between each field.

Diigo

More than your average social bookmarking site, diigo.com allows you to bookmark, highlight, and add stickynotes to anything on the web and store it for later use or share it with someone else. You can also organize this information with tags for easy retrieval. One of the neater aspects of diigo is you can create groups centered around a topic and invite members to contribute to a certain body of knowledge.