Are you new to data modeling in PowerPivot or SQL Server Data Tool (aka BIDS) or never had the chance to start with DAX, now is the time. We have released online content to help you get started in creating DAX formulas. You can think of this as DAX 101.
The QuickStart: Learn DAX Basics in 30 Minutes is now available as part of the DAX Resource Center Wiki.
Leave a comment if you have some feedback, its a online Wiki so we can change it :).