I created a Sliding Puzzle the past summer and I decided to sell it on Activeden. Activeden is a market where thousands of developers sell small utilities/games/etc and people can buy them at cheap prizes.
The process to become an author is easy. I registered, then I created a file following their “Upload” receit. You must meet some requirements as quality, clean code, good documentation of the file for your future clients, etc. Once uploaded, you wait some hours or days until they review your content. If everything goes right, your file will start selling on Activeden. If the file is not ready to sell, they will reject it until you work on it. This way they can keep a good level of quality on the site.
Once they approved my file, they set $8 as the prize for my Sliding Puzzle game. I have sold 8 times the game and I keep 50% of the sales benefit while Activeden keeps the other 50%. Up to this moment I am about to reach the $100 earnings and I will keep uploading files.
Go and play my Sliding Puzzle game!
If you want to read some more info about my Sliding Puzzle file, here is the PDF documentation.