ArcGIS API for Flex version 1.1 released

check out what is new in Release 1.1 here

check out the new added samples as well

Flex 3 Books Remommedation

Before i start down with ESRI FLEX API i had to start with Flex itself, having a Adobe Flash 8 Experience, i didn't find it much difficult, but with some new concepts and it was easy to grasp.

I would recommend the following book to anyone starting Flex 3 with Adobe Flex Builder.

OReilly.Learning.Flex.3.Jun.2008 (Read This First)
O'Reilly - Flex 3 Cookbook - May 2008
Oreilly Getting Started With Flex 3 Jun 2008


UPDATE

To get ur self more familiar with the contols and how to apply style to them i recommend the following links

Flex Component Explorer

Flex Style Explorer