Free; no registration required.

"ImageOptim optimizes images — so they take up less disk space and load faster — by finding best compression parameters and by removing unnecessary comments and color profiles. It handles PNG, JPEG and GIF animations."

"Flip Through Images is a Macintosh application for quickly displaying multiple image files."

$25 — "PTLens is software that corrects lens pincushion/barrel distortion, vignetting, chromatic aberration, and perspective."