If you are looking for custom charts in Excel, two resources that I turn to first are:
For dashboards, specifically I would recommend the six part series by Robert "Creating KPI Dashboards in Microsoft Excel" (Robert also has a blog, Clearly and Simply, that has great content and a list of other sites that you may find useful under the sidebar "Blogs and Links")
For the theory behind dashboards, Stephen Few has a book "Information Dashboard Design: The Effective Visual Communication of Data" that goes into detail on best practices. He also wrote and article about dashboards focusing on good vs. bad designs.
You may also consider taking a look at Tableau if you want the end users/decision makers making their own dashboards.