Resize Magic is an application that resizes images with a high quality algorithm, similar to the Lanczos algorithm used by other programs, with some modifications. It can be used to batch resize images, and preserves Exif data and ICC color profiles. A Photoshop plugin is also available as a commercial product.
delaboratory is an image postprocessing application. It allows you to modify the color and contrast of a photo in a creative way, using curves, a channel mixer, an equalizer, blur, an unsharp mask, high pass, vignette, dodge/burn, shadows/highlights, and blending in different colorspaces (sRGB, ProPhoto, LAB, CMYK, LCH, HSV, HSL) with floating-point precision. Each operation is stored as an adjustment layer, and you can watch a realtime preview.
Urban Lightscape is a photo filter for exposure correction, localized brightness adjustments, dodging and burning, and the introduction of synthetic lighting to a photo. A simple "double-click-and-drag" paradigm is used to place control points on a photo, and clever edge detection localises and interpolates lightness adjustments around and between these points. Results are rapid, with additional controls for more subtle refinements.