Paint.NET
Media
Paint.NET is free image and photo editing software for computers that run Windows. It features an intuitive and innovative user interface with support for layers, unlimited undo, special effects, and a wide variety of useful and powerful tools.
Perian enables QuickTime application support for additional media types. All major formats supported.
Quicksilver is a unified, extensible interface for working with applications, contacts, music, and other data.
Seashore is an open source image editor for Mac OS X’s Cocoa framework. It features gradients, textures and anti-aliasing for both text and brush strokes. It supports multiple layers and alpha channel editing.
Skim is a PDF reader and note-taker for OS X. It is designed to help you read and annotate scientific papers in PDF, but is also great for viewing any PDF file.
VLC media player is a highly portable multimedia player for various audio and video formats (MPEG-1, MPEG-2, MPEG-4, DivX, mp3, ogg, …) as well as DVDs, VCDs, and various streaming protocols.
Xee is a lightweight, fast and convenient image viewer and browser. It is designed to be a serious tool for image viewing and management, with a sleek and powerful interface.