Here are the list of free online image editors, these tools will give you the flexibility to do quick changes to your photos or images online for free.
Aviary Phoenix photo editing tool has layers, channels, levels, hue and all other features that you would expect from the Photoshop like application. It Allows you to import from photo sharing sites such as Flickr and Facebook. You can upgrade to pro version for extra functionality and storage.
Picnik allows you to import images from Picasa, Flickr, Facebook and more. It has useful tools, fonts and shapes for free. You can upgrade to premium subscription for more tools.
This tool is from Adobe, it allows you to store up to 2 GB for free. This web based image editor has limited features compared to the desktop application.
DrPic has various tools to edit and save the images in different formats.
Another free tool to edit and save your images online.