MarkPad is a simple and easy-to-use development software and application that allows users to quickly and easily create, edit, and manage markdown-formatted text documents. It includes features such as syntax highlighting, live preview, and auto-completion. With MarkPad, users can quickly and easily create and edit documents in Markdown, a simple and lightweight markup language that is optimized for writing technical documentation. MarkPad also includes a built-in preview mode, allowing users to see how their document will look while they are writing. Additionally, MarkPad also includes an auto-completion feature which helps users automatically complete any words or phrases they are typing.
Discontinued The program seems to be no longer updated. The latest version, 2.5, released in December 2014, can still be downloaded from the official website.
Great online application to edit markdown :)