postgres 9.1: both md5 and ident on the same connection type?
Only if you can differentiate by user or database. You can't have both ident and md5 enabled for the same (user,database,connection-origin) tuple.

I usually use unix sockets with ident for my admin and casual use. Many apps only work over tcp, so I use tcp with md5 for them. For apps that can use a unix socket I specify their database as md5 and just use a password when I connect to it.

It'd be really nice if Pg supported fallback auth where you could try several protocols or where the client could pick, but right now AFAIK it doesn't.