FastStone Image Viewer - Freeware -

• A fast, stable, user-friendly image browser
• Includes image viewing, management, comparison
• Red-eye removal, emailing, resizing, cropping and color adjustments
• Musical slideshow with 150+ transitional effects
• Supports all major graphic formats
  
  download here

The GIMP - Freeware -

• GIMP is an acronym for GNU Image Manipulation Program. It is a freely distributed program for such tasks as photo retouching, image composition and image authoring.
• It has many capabilities. It can be used as a simple paint program, an expert quality photo retouching program, an online batch processing system, a mass production image renderer, an image format converter, etc.
• GIMP is expandable and extensible. It is designed to be augmented with plug-ins and extensions to do just about anything. The advanced scripting interface allows everything from the simplest task to the most complex image manipulation procedures to be easily scripted.

download here

IrfanView - Freeware -

• Many supported file formats (click here the list of formats)
• Multi language support
• Thumbnail/preview option
• Paint option - to draw lines, circles, arrows, straighten image etc.
• Toolbar skins option
• Slideshow (save slideshow as EXE/SCR or burn it to CD)
• Show EXIF/IPTC/Comment text in Slideshow/Fullscreen etc.
• Support for Adobe Photoshop Filters
• Fast directory view (moving through directory)
• Batch conversion (with image processing)
• Multipage TIF editing
• File search
• Email option
• Multimedia player
• Print option
• Support for embedded color profiles in JPG/TIF
• Change color depth
• Scan (batch scan) support
• Cut/crop
• IPTC editing
• Effects (Sharpen, Blur, Adobe 8BF, Filter Factory, Filters Unlimited, etc.)
• Capturing
• Extract icons from EXE/DLL/ICLs
• Lossless JPG rotation
• Unicode support
• Many hotkeys
• Many command line options
• Many PlugIns
• Only one EXE-File, no DLLs, no Shareware messages like "I Agree" or "Evaluation expired"
• No registry changes without user action/permission!
• and much much more

download here