I came across "file thingy" a bit ago and for simple stuff like that I found it perfect. It’s just a single PHP script but easy to modify if you want to build in something like authentication back through modx.
This is not a MODx specific solution, but perhaps you’re looking for something like
Opera Unite (still in beta). I’ve only heard about it, never actually used it myself. Might be more user friendly than FTP or webdav?
I am going to have a look at Opera Unite as well! Opera keeps getting more and more useful.
The inconvenience about it is that most of my friends aren’t very much interested in learning to handle a new browser. Anyway, I can’t rely on them to get Opera.
But thanks anyway!
René