The answer to the headline question in my experience is sometimes much more than you think you can do and quite often a little less than you plan to do. It's hard to hit your mark for very short time frames.
Why is it worth becoming more intentional about how much fits into ten minutes? Think about all the people who would gladly share ten minutes with you if they were sure it would really be only ten minutes. Then think about all the spaces in your day when you could get something done - if only the "something" would fit into ten minutes.
What each of us can do in ten minutes will depend on our personal way of organizing our thoughts and our communication. The point is not to achieve what someone else could do in ten minutes but to become intentional about achieving our own ten-minute goals, especially when they are communication goals.
Take the ten-minute challenge. At least two or three times today, catch yourself with just ten minutes and use one of those minutes to focus on making the most of the other nine. When you know what you want, ten minutes is quite often enough time to make tangible progress. I turned my ten minutes into this blog entry - what will you have to show for yours?