For overall overview, see the demos by Microsoft in http://www.microsoft.com/en-us/powerbi/default.aspx#fbid=kB3LlM0Qit7
The Excel 2013 is a significantly improved tool for Dashboards and it is a serious contender of Tableau.
Here are some best well presented EXCEL BI (can not believe that EXCEL can be a BI power tool, you are thinking, right?!), take a look at these videos and you will be surprised how much EXCEL has come along.
Getting Started with Power View in Excel 2013
Relationships in PowerView Tables
Introduction to PowerPivot by Microsoft …
Using Advanced Features of Data Explorer and Building Power View with Bing Maps and Animations
Introduction to Power Map Within Microsoft BI Excel Tools