LRViewer is a standalone viewer for Lightroom image previews that also allows you to extract previews as JPEG files. It makes no changes to the Lightroom catalog, which means that it can't create any previews that aren't already present. Both the catalog (ending in "lrcat" or "lrdb") and the associated preview file (ending in "lrdata") must be present.
Home Image Effects has a great set of image effects for juicing up your photos.
