I do a lot of research online.  Having the right tool can make it much simpler.  I've been using Google Notebook for several years, and have been really happy with it.  Get the Firefox extension, and taking a note is as simple as highlighting the text/images you want to save, and right-clicking and choosing "Note This".  It will add the text or image to your notebook, and includes the URL from where you got it.  You can have multiple notebooks, for different subjects, and move or share notes between them.   You can also export your Notebook to Google Documents, and from there to Word.  Sort of silly that it's two steps, but it can be done.  You can also blog from Google Documents, so this could be a method for collecting information to blogging.

Coolest of all, you can share with others.  When my life and I plan trips, or major purchases, we'll use a shared Notebook, either of us can add information, type notes, etc.  Works awesome.  It'd be great for students or workers collaborating on research for a project.  Simple, powerful, and effective.  I love it. http://www.google.com/notebook

Zotero is another competitor.  It functions much like Google Notebook, but has significantly more sophisticated tools for tracking notations and references.  It has a considerably more complicated interface, and doesn't seem nearly as intuitive, but for people writing papers or doing academic research where a fully notated bibliography will be needed, it offers considerable advantages over Google Notebook.  However, it lacks easy collaboration, which is a disadvantage to me. 

http://www.zotero.org/

So, for casual use, collaboration, or easy integration with Google Docs, Google Notebook wins.  For academic or scientific research, Zotero is certainly worth a close look.  Anyone doing research online should be using one or the other.