Light Compressor is a simple yet powerful post processing app that lets you combine multiple exposures into a high dynamic range image, or use tone-mapping to make detail more obvious in individual images.
Version 2 internally utilizes 32-bit float per channel image representations to maintain the quality of your images and can maintain that quality in export via .tiff files (jpeg and png also available for export). If you shoot bracketed images handheld, it can also automatically align the images for you.