Student Web-based Presentations

I am seeking ideas for having students give presentations electronically. My ideal would be for students to post an electronic presentation in a secure spot (no public access without an invitation to view. I would then like these invited visitors to have the capacity to comment on the presentation and to ask the student questions - asynchronous. The visitor should be able to choose whether their comments and questions were visible to other invited guests or only visible to the student (and professor). I am a novice at this. What techniques do you suggest? What software, etc.