Flickr has teamed up with Picnik to add photo editing as a feature for Flickr users.
Choose an image in your photostream, hit the edit button, allow Picnik to access your Flickr image and a suite of editing options load.
Images can be modified with effects, shapes and frames added, color adjustment, resizing and rotations.
Here's one I prepared earlier - If you've forgotten to send a Christmas Card, turn one of your photos into a greeting and send an email...
Just be careful you don't replace your existing photo (unless you want to) and check the options before saving.