Diigo is a research tool that attaches to your web browser. You can then grab images, bookmark urls, highlight text, capture sections of the screen and organize this information in folders in a library. You can create a group for your class and share all the research that everyone does on the topic. You can also join an existing group relevant to your research. This is the Discovery Educator Network:

There are comprehensive tutorials HERE
More bookmarking tools:
Delicious http://www.delicious.com/
Google bookmarks http://www.google.com/bookmarks