Just to add a little note: back in May I did some work on multidb,
some thoughts and some work can be found on http://trac.woe-beti.de/ ,
which Ben Ford set up for this.
I stopped because django was becoming too much of a moving target to
keep it in sync (and i did not have the time).

I would like to point out that my starting point was mainly to be able
to use data from different database ENGINES (like some tables from
postgres and some from mysql).

As far as I can tell, this is not supported currently by the plumbing
Malcolm provided (since the operations settings eg in WhereNode are
taken from the default connection and not from the passed in
connection; this is no problem if your databases are using the same
engine, but it returns wrong SQL if you have different engines).
I allready reported this once in #7258 (which was considered invalid,
probably because I forgot to mention my use case).

Anyway, I am very glad to see some renewed interest in this field!

Koen