Ask HN: What tools do you use to improve your presentation skills?

[iltaiuti]

Are there any online tools or portals you would recommend to improve someone's presentation skills? Any specific courses? And what are their drawbacks?

Context: I often see developers who are extremely skilled give poor presentations. These performances seem to ruin an otherwise stellar content. Although there are many companies who do offline (in person, 1 to n) training, it would be great to have your input on tools which achieve the same or better, but online. Thanks!