I keep re-creating this from time to time, so I thought I would put it up for others to use. This is a very simple style for rounded gel-like buttons (shown here magnified 3x, but the style works OK for buttons of various sizes). The left-most one is the “normal” style, the middle one is mouse-over and focused, and the right one is disabled. These are great with a slider to create “zoom” type controls, or for play/pause buttons etc.
Source Xaml