CuteMarkEd is a markdown editor

CuteMarkEd

Text editor in Markdown
Live preview
Can export in HTML and PDF

http://cloose.github.io/CuteMarkEd/

It is much more powerful if used along with:

EMA

A simple, personal wiki that can be installed both in Windows and Android devices. All installations are kept in synch throuhg a Dropbox account.

Its author says that "it is free and open source". The source can be found on github.

http://jwbs-blog.blogspot.mx/2010/09/ema-personal-wiki-for-android-and.html