If you conduct a lot of research for classes that you are taking or teaching, I must suggest Zotero, a smart Firefox plugin that allows you to collect, manage, and cite your sources without leaving your browser. As a Ph.d student, I write a lot of papers and about to begin my dissertation (once I can decide on a topic). One of the things I dislike the most is making the bibliography pages and citing all the reference in correct APA format. Zotero is my answer. If I am reading an online book, I hit Zotero and it automatically finds the necessary information I need for my references. Not only does it find it, it creates the reference lines I need so I can simply copy and paste it into my bibliography.

According to their site, here are some of the features Zotero has are the following:
•    It automatically capture citations
•    Organize with collections and tags
•    Wide variety of import/export options
•    Create and access your Zotero library from anywhere
•    Remotely back up and sync your library