Topaz Adjust is one of my favorite plug-ins. It's not a true HDR plug-in, but it can expand the dynamic range of an image - with a click of your mouse or a tap of your stylus.
Here you see how a relatively flat image (bottom) was transformed into a much more dramatic image using the Spicify effect in Topaz Adjust. Also notice how the washed-out floor in the bottom image has more detail and color in the top image.
When using Topaz Adjust, take the time to adjust each slider - especially the Noise slider, as the Topaz noise control (also available in a separate, more sophisticated plug-in, Topaz DeNoise) is one of the best noise reduction methods out there.
You can learn more about Topaz Adjust and other plug-ins – and get discounts on some plug-ins – at the Plug-in Experience.
While you are on the Topaz site, check out the Photoshop Bundle. It can save you a bundle!
Explore the Light,
P.S I am giving a HDR talk at the Apple Store in SoHo in NYC on April 7th. Hope you can join the fun.