If your looking for something simple and easy, this site is great. I made these two collages below to show you the before and after effects.
The first photo we took in the car and didn't realize the camera was zoomed in. I actually like how it turned out but it was way too light. I don't remember what I did but I played around with the exposure, shadows, and contrast.
The second photo was too dark. I lightened it and adjusted the color vibrance and exposure.
Nothing too fancy but a great site with easy to use editing tools. Give it a try!