App with different homepage per domain

I've been addressing the same problem as you for about the last 7
months. I don't know what the business aspects of your desire are, but
there's a long way between now and getting it done. The basic approach
is to have all database tables as children of a "MAIN" table. When the
request arrives you 'scope' on the to call the
appropriate 'main.subtable.find(:all).
I can't tell you the PAIN it took me to ferret this out.

This thread may help