We recently set up a small support group in Globoforce for people trying to improve their presentation skills. We meet regularly and people give lightning talks on any topic they want. The time limit is ten minutes followed by feedback from the group. Part of the development process is videoing the talks so people can judge their own performances.
Here's a recent one I gave on the Seven Stages of Action as described by Donald Norman in his book "The Design of Everyday Things". Which is, of course, an essential read. Grab it here. Apologies about the flickering screen. If anyone knows of a way to remove it, let me know!