I don’t know of any reputable and free online writing courses, but I do know of some that are very reasonably priced and are very good.
You can learn about business writing and get some practice through online-learning.com. This excellent program offers a variety of writing courses and also graphic design.
From the online-learning.com website - see below:
Our mentored courses are designed for people who want to combine the convenience of online learning with hand-marked assignments, personal support, and feedback from expert instructors.
These university-accredited courses provide you with the skills to write and design technical documents, business letters, reports, proposals, web pages, help systems, single source documents, and online courses.
You can choose to take an individual course or you can choose courses from our Information Design program and become an Information Designer.
There are also some self-paced courses for people who like to learn on their own.
You get what you pay for!
If you want to find something that you don't have to pay for, you will likely be disappointed in the result. People who offer value want to be paid accordingly. And you must simply accept that.
It is much the same as deciding to follow up on the scam to get yourself a free online degree. You get a piece of paper that is worth nothing - exactly what you paid for it.
So, if you are looking for value, you are not going to find value in the free online writing courses that you think you can find.
Instead, look for value - a quality online course that you can be sure of. Find others who may have taken the courses from the same company. Find a course that is university accredited. That provides a solid reference to begin with - and you know that you will be successful.
Expect success! Work hard for it! You should not expect to sail through a class with top marks just because you are taking the class online. A reputable instructor will want you to achieve something worthwhile before providing you with the successful conclusion.
You can, of course, sign up for a university or college credit course - and earn credits towards a university degree or a college diplome.
You can also sign up for a certificate program that will provide you with a shorter time span and an introduction to the topic you want. A certificate can be a good entry to either another course or to an entry-level writing position.
So be diligent in your search for an online writing course, and you can move forward towards your goal of becoming a successful writer.