Fade to Nothing

Unfortunately, in Illustrator you cannot create a gradient that goes from a color to transparent as you can in Photoshop. To work around this, create a gradient using the color you need plus white. Fill the object with the gradient and then create an opacity mask to gradually change the object to transparent. To do this, create a rectangle slightly bigger than your object and position the rectangle over the object. Fill the rectangle with a black-to-white gradient, positioning the black over the area of the original object where you want the gradient to be see-through. Select both objects and from the Transparency palette (Window>Transparency), use the flyout menu to choose Make Opacity Mask. If you need to adjust the effect, click on the mask thumbnail (that's to the right of your object) in the Transparency palette and then adjust the position of the rectangle and/or the gradient. To return to regular editing, make sure you click on the object's thumbnail (that's to the left of the mask) in the Transparency palette.