Image Eye is a fast - and free - image viewer with a nice clean user interface.

Feature high-lights: - The only image viewer you need for viewing and browsing images. - Clean with no unnecessary menus and toolbars wasting your desktop space. - Uncompromising with the image quality. - Small and very fast, highly tuned code. - Reads all common image file formats. - Easy to rotate, mirror, zoom, pan, and adjust contrast, brightness, sharpness, hue, saturation, gamma, et c. - Image adjustments can be saved non-destructively and automatically reapplied when you next open the image. - There's an image index feature with very fast thumbnail-icon creation. - It does not attempt to be a half-baked editor, format converter, or media player. - It does include a simple slide show scripting language. - The user interface has been translated to several languages. - Freeware!

Features for the tech-nerds: - Asynchronous file I/O allows decompression to start before file reads finish. - Speculative decoding & caching of images in the background. - Data parallelism exploitation through the use of SSE2 and SSSE3 SIMD vector-instructions - Task parallelism exploitation through extensive multi-core support. - Hand tuned code optimizations for critical paths in assembly code or using compiler intrinsics. - High quality resampling (image resizing) using Catmull-Rom interpolation. - Extensive text meta support.