bubbl.us is an easy to use site for quickly adding and mapping ideas. Maps can be saved or exported as an image (JPEG) file.
padlet (formerly Wallwisher) is self described as "paper for the web". Comments and ideas can be instantly captured on a topic. Contributions can be anonymous if needed. You can try this tool out here.
Realtime Board is described as a "white board" for your browser. This tool is a bit more complex to use. But it does tie in to Google Drive. Boards can be shared for collaborative work. They can also be downloaded as an image (JPEG).
spiderscribe.net is an easy to use brainstorming tool. Multi-media elements such as text, files, images, maps and calendar events can quickly be added. Work can be shared for collaboration, downloaded as an image file (JPEG) or printed.
TodaysMeet is a great tool for capturing ideas, comments and questions in real time. It's also easy to set up and use. Try it out here. No registration required.
Prezi is typically thought of as a presentation tool. But text, files, images and videos can easily be captured and organized in the work space. Prezis can also be shared for collaboration, saved, printed, etc.