Pointy Haired Dilbert (PHD) is a blog which helps you with Charts and Excel tips. Though you can create charts directly in PowerPoint, many people do create charts in Excel and knowing how to use Excel is always a good skill for a presenter.
This blog basically helps you become better at charts. For example, see this link: Create a Dynamic Chart in Excel in 2 minutes: A decent trick which is very easy to create. Also see this or this post; Making Dynamic Charts using Data Filters or this; Compare one value with a set of values. The blog also has a Chart Doctor series wherein you can submit your actual chart (which might not be so good) and they will work on it and make improvements.
There is more. Do you want to create Venn Diagrams for presentations? You can learn how to do that here.
This was my second post in the series: 'Be a Charts Champion'. Check the first post on Juice Analytics here. If you know of any good resource on Charts and Graphs, leave a comment. And yes, remember to check the Pointy Haired Dilbert out!