Readers of this blog know I use HDR processing in many of my images. My current personal choice for processing software is Nik HDR Efex Pro, but I have also used PhotMatix and found it to be a quality product that I can easily recommend.
Link here for a review of the latest PhotoMatix version that I recently came across. It's written by Scott Bourne. If you are considering purchasing a plug-in for HDR processing, it is worth reading.
While you are there, explore the rest of Scott's site. It's dedicated to the three things that make digital photography so innovative: HDR, panoramas, and time lapse.