For example, one of the solutions is to have a question box for the students. You could have the traditional paper/pencil approach or you could use lino, an electronic bulletin board where collaborators can add sticky notes to the board. You could create a board for the class or a specific topic and have students attach a sticky with their questions. You could also use this for quick response answers from your students.
Another idea that came to my mind related to the KWL chart. This year through Google Docs, we have access to Lucid Chart. This online tool allows you to create mind maps, flow charts, venn diagrams and more. You can then share the chart so others can write on the same chart. As a teacher, I could create a KWL chart for a new topic, share it with the students and have them fill in their responses. I could then project the chart so we could quickly see everyone's responses and discuss the common ground we all share and the questions we want need answered or clarified.
One final idea, relates to the idea of group work and the students presenting information to each other. Traditionally, the students would have created a slideshow of some sort to present their information to the class. This was a good start, but usually one student did all the work on creating the presentation because they could all work on the same document at the same time. With the introduction of collaborative tools, students can now share the work load. Google Docs offers a presentation tool that would allow students to work on their slideshow all at the same time. Gone are the days of one student typing in all the information. Now everyone in the group can add their contributions at the same time.