I have been using Powerfolder for some time to sync folders across platforms and it works pretty well (with some qualifications: I have had some strange issues but their support via chat is pretty good).

One reason I like it is that it is very customisable and they don't try to force their cloud services down your throat: I have my own server at home with no need or interest in cloud backup. I also don't like the idea of storing my data, much of it confidential, on servers that other people have access to.

In principle Powerfolder might be got to work on maemo, as it is a java app and there is a linux version. But I haven't bothered trying as I suspect it is too resource hungry for the N8xx/N900.

What alternatives exist if I want a folder that is always synced (two-way) between one maemo device and any number of other mac/windows/maemo devices I choose? I am aware of the existence of rsync but have never used it and have no idea how to write scripts to set something like this up - I am not even sure if it would be possible to write scripts with rsync that would do what I want.