Our classrooms at NUS are equipped with projectors and computers, so we can use Internet tools in class too. In next semester's first seminar, there is a graphic like this.

The task that gave me some headache.

The task is to put in adjectives that describe Geruch (i.e., smell), Geschmack (i.e., taste) or Geräusch (i.e., sound). I could use it with a transparency, but my handwriting is extremely messy, esp. when I use OHP pens. So, I started looking for an on-line solution, and found one.
Scribblar.com offers interactive rooms with an whiteboard in the middle. All people who access this room can draw on this whiteboard. So, I've put my image there:

The graphic on the whiteboard

For drawing, a number of tools are offered . Besides an selection tool, a free-draw tool (doodling), a text tool, line and number different shape tools are offered. As everyone, who accessed the room can see the drawings live, the highlighting tool can be quite useful too. The stamps offer a number of shapes such as stars, TM etc.

Tools (left) and room options (right)

On the far right side, the room tools can be seen. The admin of the room can "broadcast" her/his voice while in the room. The others can use text-chat (bottom). Assets are additional content (e.g. graphic files).

Room tools

After a shape is drawn, there are a number of options offered, which can be seen in the following picture.

Object options

Besides the usual cut, copy, paste, back, repeat and delete options, objects can be flipped, locked or unlocked (useful, if you have a background image). Furthermore the active or all pages can be cleared. If you want to show something, the pointer tool is most useful. A grid is offered, making drawing a bit easier. If you have to put in a mathematical function, it can be added using LaTEX syntax. Unfortunately, it doesn't offer a function like this on-line editor, so probably use such a service, if you have to include a function and copy-and-paste the LaTEX-Code. Finally, articles (containing definitions etc.) can be included using Wolfram Alpha. In the free version, however, only few articles can be chosen. Using queries to find information, you need is an option of the PRO version.

Multiple pages are supported

As pointed out earlier, multiple pages are supported. Hence, one can have different "slides". Adding one is quite simple: If I'm on page 8 (my last page) and want to add a ninth one, I just click the "next page" button.

Scenarios for educators

Webinars. Your seminar is on-line, students attend the seminar in the room. You "broadcast" your content, so they can hear your voice. Questions can be raised using the text-chat. If you want to offer the possibility of students ASKING questions instead of using the chat, you can also make a skype conference call (up to 25 people).

As a whiteboard in the classroom. Instead of using PPT, or Prezi, you can add text freely in the presentation without leaving the presentation mode. So, you can be more interactive.

Screencasts. You want to make an educational video? Scribblar offers you the opportunity to design the "slides", you can record the whiteboard only and make a screencast.

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Scenarios for students

Project meeting. You want can't meet in real life, but have to discuss a project? Scribblar can be used for meetings.

Tuition. You can also use this for tuition purposes.