4: Photo Retouching
You can sell photo retouching services at various websites. You can also work as a freelancer at odesk.com, freelancer.com etc.
In those websites, every day there are dozens of project or job requirements gets submitted there and all you need to do is to apply to those projects.
You can also use microlancer.com and and sets your rate there.
My Judgment: Usually these projects are time consuming and you need to apply to these projects only when you have sufficient time and you can manage to complete the projects within the deadline.
Also Read: Best 7 Books to Learn Adobe Photoshop
3: Create Video Lectures
Nowadays, people prefer to watch videos rather than reading books and photography is something that would be easier to learn by watching videos.
So you can take advantage of this market requirement and create a series of video lecture. Being a photographer, I guess you already have a DSLR. So there is nothing to be done in terms of money. Use those DSLR cameras to record videos and create a series of videos.
Upload those videos to online video tutorial websites like Lynda.com, Udemy.com etc.
My Judgment: Creating a video lectures can be a tedious task and you always needs an assistant with you to record the videos and so on. Apart from these, you need to have a strong experience in photography.
2: Organize a Webinar
You can organize a paid webinar and publicize about it everywhere. All you need to do is to create a nice presentation and think about the ideas that you are going to share in the webinar.
If you are not a well known or skillful photographer, I suggest you to keep your rate low (like $29 or something). However, if you think that you have a lot to share and you photography is amazing, you can charge them as high $99 or $199.
My Judgment: Make sure that you have practiced the things that you are going to say during the webinar because once you teach or say something wrong, people will have a wrong impression about you and probably they will not register for your next webinar.