In the past I have used phpWebSite, with the phpwsListings module, in
the past. 

One problem we encountered was that the phpwsListings module is
out-of-date, and has not been kept inline with core phpWebSite
developments; the result was that we had do some work to bring it up to
scratch for our purposes.

Is there some other OS system that could be recommended? It's for a
rent-a-cottage type site.

Requirements are:

*       Open Source
*       designer-friendly templating system
*       user-friendly listing uploads
*       comprehensive user-permissions system (the idea is to allow
registered users to create their own entries)

Thanks,

Daniele