Windows only: LightBox is an extremely user friendly tool for editing photos when you need more than a simple crop and resize but less than a full-out Photoshop massaging.
How user friendly is LightBox? When you run the program you're presented with a sidebar of common tasks like colour balancing and red-eye removal. Mousing over each of them provides not only an explanation of the tool but sample pictures showing the results and every tool within the editor itself has mouse over tips. Once you're actually editing your image you can easily—as seen in the screenshot above—divide the image to show how the alterations are effecting it compared to the original. The divided and side by side comparison feature is great for photo enhancements where your goal is to make the picture more appealing without giving it an unrealistic appearance. If you need additional functionality, there is a Plus version available for $US19.95 which adds on features like masking and auto colour correction. The basic version of LightBox is freeware, Windows only.