Windows/Linux/Mac: Freeware app XnView gives you incredible control over editing digital photographs in a lightweight package. Similar to Lifehacker favourite IrfanView, XnView is fast and can import and export hundreds of image formats. It also features lossless rotate and crop, filters, colour modifications, red-eye reduction, and slideshow view. Categorize images and easily access EXIF meta information. Beyond image editing, XnView is a solid choice for making life posters. XnView is freeware for Windows/Mac for non-commercial use only (and completely free for Linux).