I also use Zim. The nice thing is that Zim uses plain .txt files without the need of a database. So you can also view and edit your notes/pages using any text

I also use Zim. The nice thing is that Zim uses plain .txt files without the need of a database. So you can also view and edit your notes/pages using any text editor instead of Zim itself. Making backups is also very easy this way. I keep these text files in sync across my devices using owncloud. That way I can also use it on my smartphone by just viewing the plain text. No extra apps necessary.