We all like extra cash, specially if it comes from the Internet. Because many people has access to this communication media. If you’re good using Adobe photoshop, the following advices will be great for you:Create brushes or any other resource for Adobe Photoshop:
As we all know, you can’t ever have enough brushes. People’s always looking for more brushes for Photoshop. This is a great way of promoting your blog or website.

Create your own article shop online:
There’s a friend of mine that uses CafePress and he just told me that his sales are going really well with it. Remember the world is full of different people, thus different tastes.

Participate in contests:
Some people like to participate in designing contests. Others don’t because the creators of the event will have rights over the winning design. Taking chances from time to time won’t kill you.

Write your own tutorial:
If you have a blog or a website, and you’re good creating fool-proof Tutorials, you’ll be able to increase your monthly income big time!

Sell your photos:
There are millions of web pages that will try to sell you pictures. Sometimes they even pay you a commission for every download they get. Among them are Fotolia and Shutterstock.

Source:  Photoshop Roadmap