Having now both a new Mac Book to play oolite on and my desktop computer that is also used for Oolite, I wanted to synchronise my versions.
Easiest seemed to use my Synology nas. Since this spring, the nas software also contains a Cloud Station. I created an "AddOns" folder on the nas, put all my oxps in that folder and than subscribed my computer AddOns folders with this one. Whenever I change something in an oxp on one computer, that change also happens on the other computer. So I am sure I always play with the same oxp set on both computers and don't forget to update an oxp on one of them.
Just noticed one problem on the lion OS. My AddOns folder is in the library. The libraries are hidden. But, to link the cloud to the local AddOns folder, I had to select it through the file dialog. I did see no way to make the library visible in the file dialog. But, by adding the AddOns folder first to the favorites (on the left), I could select it there and the path to the hidden library was stored.