I want to create a new icon for my application according to the new Android Design Guidelines. Is there any way to get my 2D silhouette and automatically extrude it to create the 3D effect?
Before you get into extruding your icon, it's worth considering that a) you only have a very small number of pixels to play with (3 at the most, really), and b) there are very, very few Android app icons that use (or fake) extrusion to create the illusion of depth.
The guidelines call for dimensionality, and there are many effective ways to achieve that without getting into Repousse, which is only available in Photoshop Extended.
If you have Extended, here are the steps:
If you don't have Extended, you can quickly create a simple faux extrusion by duplicating your icon layer twice and moving the copies below the original. Nudge the upper copy up and right one pixel, and the lower copy up and right two pixels, then merge the two layers. Darken the visible part of the merged layer with the Burn tool or use a Levels adjustment. (If you need more "extrusion," make more than two layers, but I wouldn't go beyond three for an icon.)
Go to Filter, Stylize, Extrude. It will only work on RGB images. If you're using a CMYK file, change the Mode to RGB, extrude your image then convert the project back to CMYK for print, if necessary. I don't know about getting it to automatically extrude. Look at the 3D options, under 3D, and the option there, to Browse 3D Content Online (last on the pull-down menu).