I am certainly not the best person to come to when discussing artistic design, but I did want my buttons on my calculator to have a little more pizzazz than the plain old boring gray android default buttons. After perusing the web a bit, I found a really nice tutorial using Gimp (an open source image manipulation program, read: free) that even I could follow along with.
Round Web 2.0 Button is a tutorial at mygimptutorial.com that takes you step by step through the creation of a button with a 3d effect. It points out brushes, effects, colors, and even pixel placement at times. I had to veer very little from the instructions to make a button to suit my needs. The only mention I could find of the author was that it was posted by a user named yay in 2008. So, thank you Yay, for the wonderful lesson in image manipulation.