Photon

Photon... Designed for both professional photographers and advanced photography enthusiasts, Photon is a high-performance digital photo workflow application that makes it easy to review and organize large numbers of photos.
Photon focuses on the front-end of the photo workflow process: ingest, review, and culling.

Unlike other photo management applications that often require lengthy import steps before reviewing and organizing photos, Photon's intelligent on-demand caching engine makes full resolution views of your digital photos available within seconds. Additionally, Photon's innovative "stacking" feature streamlines the process of organizing large batches of images by making it easy to quickly shuffle photos into separate stacks using a single keystroke.
Your time is precious. Why spend it waiting? Download the free trial version and start organizing your images with Photon today!