One that you could try is rsizr. It will immediately prompt you to open a image file to edit. You can easily resize and crop any image file you uploaded. Rsizr use a special technique to keep the quality of the image edited. You may experience image quality loss, blurred text after resize, but not with rsizr. I have tried rsizr with 800 x 600 image, it resizes the image from 191kb to 121kb. After editing, the image can be save directly to your computer, or to your ImageShack account.
Another one that you could try is flauntr. Flauntr have a lot of feature for image editing. Just enough to make you comfortable without Adobe Photoshop. You can change hue/saturation, brightness, resize, crop, and you can also applying effects to your image, for example blur, greyscale or sepia. Give it a try 🙂