Stock image distributors often request "unsharpened" digital files. It might be better to request no sharpening beyond capture sharpening, since online catalog images need to look reasonably sharp. Most raw processing software applies a certain amount of sharpening as a default, although you can usually adjust this or turn it off. Some photographers, worried there will be no output sharpening, increase this somewhat when processing raw files. Every stock distributor should educate clients the best ways to sharpen images from their collection, since digital images will only look their best when sharpened specifically for the type and final size of output.
Magazine publishers usually specify unsharpened files, as well. But a small amount of capture sharpening will do no harm, while neglecting to sharpen will definitely affect printed quality.
Publication designers and web designers vary in their understanding of sharpening. One possible strategy is to deliver layered TIFF or PSD files at or near final size, with sharpening applied to a duplicate layer, and a ReadMe file and/or delivery memo explaining the layer. Name such a layer "sharpening." Fuzzy pictures on the web often result from extreme down-sampling of large camera files. One strategy is to deliver smaller files to web designers, typically in the 1024- to 768-pixel range for height or width, and apply a degree of sharpening that looks right at that size. Better web designers will request no sharpening beyond capture (or raw conversion), but will indicate they plan to sharpen appropriately as they resize.
Sharpening is a very complex topic. For a more complete discussion, see Bruce Fraser's Real World Image Sharpening, Peachpit Press, 2006.