Trailfire lets you compile a list of websites in a trail that you mark and can leave notes on. I can see this tool being used to create a guided scavenger hunt where I direct students to the site and put the question in the notes like a webquest. I could see using this to introduce/guide students in research on a new topic. You also can see trails created by others and learn from their journeys.
Bubbl.us is a simple tool for making graphic organizers. What I liked about it was that it was easy to use and could be used by students or teachers. It also can be printed or e-mailed.
Knowtes is an on-line flashcard maker. I give this site mixed reviews. When browsing the catelogues I did not find many useful cards already created. Many of them were just titles with no cards in them at all. So you would need to create your own cards. I did not try that feature as I did not like the site that much. Also you self-report if you answered the card correctly. I can see students just fast-clipping on the right and lying to say they got them all right if they did not feel like trying.