Design web images. By pairing good aesthetic sense and the use of design or photo-editing software, you can make and sell background graphics for social media pages, web logos, or computer icon packages. If you know or are willing to learn computer programming, seriously consider making web pages; programmers may be easy to come by, but programmers with an eye for beauty are another thing altogether.
Teaching and tutoring English as a second language is a great way to make money online, not to mention open some doors for you to travel the world if you'd like. While full ESL (English as a Second Language) accreditation is recommended, as long as you’re a native speaker and have the ability to teach, there are people in countries such as Hong Kong or the UAE who are willing to pay upwards of $25/hr for you to tutor them English via Skype. Check out Indeed, Learn4Good and Remote.co for remote english tutoring jobs or sign up on a specialized site like VerbalPlanet or Chegg Tutors.
Consulting is good work, if you can get it. Consultants give guidance to companies looking for help with everything from marketing to environmental remediation--and for that they clock an average 10% operating margin. Many consultants can easily work from home when they're not with clients on site, and most charge on a per-project basis rather than by the hour. Two big challenges: marketing and pricing the service. For more on the first, check out "Twelve Innovative Marketing Techniques"; for more on pricing, try "How To Figure Out Your Daily Rate."