Fotor.com is online photo editor that is pretty powerful for what you can use for free.
The site can be used without registration, and offers three modes: Edit, Collage, and Design. For each mode, not all of the features are available for free, but those features are identified with a little diamond flag. This is nice because it saves you from accidentally selecting a feature that you can’t use.
Edit mode is used for touching up photos and offers some addition tools like adding text and stickers. Collage is used for combining multiple images into one. And finally, Design has several templates and social media sizes to use as a starting point for a new image.