Here are some ways I have found that people make money online via twitter:
Virtual Brand Management
Think of a brand as a name plus the reputation that goes with it. When you think of Linda Ikeji the first thing that comes to your mind is celebrity gossip and human angle stories in the same way regular businesses want to have a certain reputation associated with their name and many of them have taken to twitter to sell their images/brands to active twitter users.
This has created a lot of opportunities for creative thought leaders on twitter to promote businesses and their brands to their followers. An example of someone who does this really well in popular political blogger Japheth Omojuwa whose twitter handle is @omojuwa. He gets paid by big business brands to promote them to his followers and his earnings runs into several hundred thousands per month.
Social Media Marketing
If you know any business that has products to sell you can go online with your craft and make cool cash for yourself by marketing their products and services to your followers. You earn a commission on successful purchases made through you. So you for instance could do this with real estate or cars as the case may be, just look inwards and search for that business idea/opportunity you can market online via your twitter handle.
Are you looking for cost effective ways to market your products and services online then send an email to: email@example.com [serious enquiries only please]