Flex has always provided rich functionality for customizing the appearance of its built-in components. You can start with the default appearance of the components and extensively tweak their properties through CSS styles, or you can completely replace the default appearance by drawing custom vector or bitmap skins using visual design tools, such as the tools in Adobe Creative Suite.
In today post, i will show you some tutorials where you can find information, tips and techniques to get your Flex application look better. You might want also to check my previous Flex Skinning Post with more Tutorials.
1 – Flex Quick Starts: Building an advanced user interface
A quick how to tips article pointing you several examples of skinning in Flex.
2 – Skinning in Flex: Beauty is Only Skin Deep
In this Yahoo Flash Developer article, will be demonstrate how to create a simple skin element in Flash for use in Flex Builder. With this skin, you will style the Button element with our own simple color design.
Awesome article from the very known flex skins site scalenine, pointing 10 techniques for skinning.
4 – Degrafa component skinning (Video Tutorial)
A screencast walking through the process of creating custom skins using Degrafa, Showing you how to get set up with the Degrafa SWC and how easy it is to start creating via Degrafa MXML.
5 – Flex Skinning: Introduction w/ Buttons
2 parts extensive tutorial, explaining you how to skin a button component.
6 – Using FlexBuilder 3 and Flash CS3 to Build Your Skin in Flex–KingnareStyle
A step by step tutorial teaching you how to build your beautiful skin.
7 – Jumping Into Skinning with Flex 4 , Gumbo (Flex 4) Skin with Transitions
Again two great articles from the king of Flex Skins (scalenine.com), this time on the next coming release of Flex 4;
8 – Designing Flex 3 skins and styles using Creative Suite 3 and Flex Builder 3
Great Adobe Dev Tutorial, by Narciso Jaramillo that provides you an overview of the CS3 extensions and Flex Builder 3 features that automate the skinning and styling workflow.
Tagged: adobe flex, gui, how to, Interfaces, Skinning, Tutorials 
