If you are a Flickr user, you may have noticed that you can edit photos right in your browser using Picnik. You can also use Picnik by itself, but it is especially nice to be able to upload your photos just once.
Pro tip: most photos need some adjusting. Some cameras are better than others, but this holds especially true for cell phone cameras. If you want to enhance color with minimal fuss, use the “auto-fix” button to spruce up your photos.