I recently downloaded the Picasa2 photo organizing and editing software by Google. It so amazingly simple and elegant. All the usual photo editing options are their plus the power of Google indexing! Just as the Google search site's "I'm Feeling Lucky" button usually gives you good search results, Picasa has a "I'm Feeling Lucky" button that automatically adjusts brightness, contrast, color temperature, etc and it usually does an excellent job.
If you haven't already done so, download it now, you won't regret (they even have a Linux version!). Click the link on the left side nav to download it.