Any of my photographs that I think will sell I'll put on my Shutterstock profile. Unless you're able to do freelance work for clients online, your best be of making money is to sell your stuff on sites like Pond5, Shutterstock, Istockphoto, etc.
I only sell on Shutterstock, but its nice because when your photos are accepted and put online, all revenue is passive. You don't have to do to earn from it, it just come as people download your work. My portfolio only has about 40 images, so I only make around $0.35 to $0.60 every month on sales. But if you really buckle down and put together a large and impressive portfolio, you could easily be making good money every month from your photography.
Shutterstock application process are somewhat lengthy you have to submit 10 photo's and it must be approved by a reviewer in order for you to be accepted and be able to sell through them.