RealWorld Photos 2013.1 is a capable and easy-to-use photo editor which is optimised for web publishers.
The program has many batch processing tools. Select a group of images or folders and you can have it resize them, correct colour and contrast, apply effects, add watermarks and more.
Better still, areas not touched by a particular operation won't be re-encoded. Add a caption to the bottom of an image, say, and only that area will be altered, keeping any loss of quality to an absolute minimum.
The program is unusually convenient to use, as it's available in a portable version, and runs on anything from Windows 2000 upwards.
Version 2013.1 adds many enhancements, too:
•Shape tool for creating shapes and selections from Bezier arcs.
•Image brush now respects active color if the pattern is monochrome.
•Polygon tool with configurable start shape.
•Out-of-canvas content supported.
•Effects automatically remember up to 5 last configurations and allow you to return to them or to reset values to defaults.
•Color picker and fill style selector were merged and simplified.
•Redesigned tool configuration panels.
•Two-column window layout with Layers panel on the left side and a new Media panel on the right side.
•More types of downloadable media packs and easier application of downloaded styles.
•Improved .psd import - vector masks are imported as vector layers.
•...and many minor improvements.
RealWorld Photos is a powerful tool, but can be complex to use, and it's arguably a little expensive. Even purchasing a $29 licence doesn't allow you to use the product commercially (you'll need to spend $59 for that).