Ebook: Foundation Flex for Developers: Data-Driven Applications with PHP, ASP.NET, ColdFusion, and LCDS

This book a great way to get you working in Flex fast... if you already have a good understanding of AS3 from a Flash background. If you're not familiar with AS3 than there are some sticking points that slow you down. But if you're goal is to transition form working in Flash to working in Flex, then this book is an excellent place to start.