Do you have a hard time choosing the appropriate visualization for your data based on the goal of the visualization?
Then this excellent graph selection matrix by Stephen Few may be of help when building your dashboards.
Also of interest are these design examples that show (interpretation) issues with particular visualizations and proposed solutions.
If you want to create useful and professionell charts in Excel maybe the Add-In “OneBoard” is quite interesting: http://www.pmone.de/en/products-solutions/visualisierung-information-design/oneboard/chart-library-screenshots/
If you are interesting in a excellent visualisation concept for business graphs, you must have a look at www.hichert.com!
This is also helpful with great examples.