Which tools help with your Zettelkasten system?

I'm reading 'How to take smart notes', and intend to implement the work flow within. I'm not an academic, and not planning to write a book. I just want to get more value from the time I spent reading and thinking.

What tools work for you? I know Zotero is the go-to tool for references.

I'm not sure which tool to use for the slip-box. I'd love something that:

- Has a GUI or at least ncurses interface

- Doesn't require familiarity with emacs

- Stores things as plain files (which can be versioned with git, or synced to a cloud filesystem)