iPhoto Batch Enhancer is a handy tool that allows you to apply iPhoto's built-in effects to a group of photos, instead of just one at a time. One feature specific for users of iPhoto 5 + 6 is 'Snapshot', the ability to quickly record the slider positions of iPhoto's built-in adjustments panel and save them as a batch adjustment setting for later use. iPhoto Batch Enhancer also works with RAW images so it looks like it can work on just about any format compatible with iPhoto.
Compatible with versions 2-6 (the latest) of iPhoto, this handy tool is also a Universal Binary for all the Mactel owners out there. iPhoto Batch Enhancer is donationware and available from feroXsoft.