I've recently been porting graphserver to postgresql.
I did not test everything so there might be bugs hidden somewhere. But
for the stuff I'm doing with it it's working fine.
You can have a look at it at: github.com/tomco/graphserver
If you are using the port everything stays the same except that you
won't give the command line tools a path to the sqlite file but a string
to connect to the database server. So you would do something like this:
$ gs_gtfsdb_compile transi_data.gtfs "dbname=test user=postgres
password=secret"
greetings