http://vector.tutsplus.com/tutorials/text-effects/how-to-create-a-semi-transparent-3d-text-effect-in-adobe-illustrator/

In the following steps you will learn how to create a colorful, semi-transparent, three-dimensional text effect in Adobe Illustrator. We’ll start with some basic text and several Compound Paths and a built-in Calligraphic brush. Once we get our starting vector shapes we’ll add the three-dimensional look using the Extrude & Bevel effect. We’ll use some simple vector shape building techniques and masking tricks along with some basic effects and blending techniques to give our three-dimensional shapes a semi-transparent look.