<p>I'm mostly a .Net person at the moment, but I've been playing with Java some lately-- exploring what's out there.</p>

<p>Now I'm looking for the Java equivalent for WPF.  I know I could find an OpenGL library or two out there, but that's not really as rich or simple as the WPF system.</p>

I think a combination of JavaFX, Swing, Java2D, and Java's browser-based JRE comprise the solutions that WPF provides:
JavaFX applications (actually, any Java app) can run in the browser or on a desktop
JavaFX provides high-end video support
JavaFX provides for scripted animations and visual special effects
Swing provides UI capabilities, and can be used in both Java and JavaFX
Java2D, which provides the underpinnings for all drawing tasks (including Swing), takes advantage of hardware acceleration and DirectX support
The JRE on the desktop or the browser enable Java applications to be deployed to multiple environments (including other screens, like set-top boxes or phones)