A person that writes for another person's blog under their own name is called a guest blogger. A writer that writes the blogs as the blog owner is called a ghostwriter.
A blogger is a person who runs and/or writes a blog (weblog).
Usually someone who writes on a blog that isn't theirs is called a contributor or a guest blogger.
Testator.
The person who writes a check is called the payor. Or in the case of my brother, a sucker, when he writes another check for his girlfriend.
An author.
a publisist a bigraphy
composer
a playwright
This is a poet
A person who writes newspaper articles is called a journalist or a reporter.
A person who writes newspaper articles is called a journalist or a reporter.