08 "plain" (or "boring", whatever you prefer) S60 with 55k miles, I used to have a lot of these problems also, rattling glovebox, creaky seats when turning, armrest squealing like a little pig, dash rattle when going over bumps, and door panel noises. Now I have none (except the rear deck rattle that only shows up when I am having a bad day), so i'll run through what I did one at a time.
Glovebox: there is a piece of either wood or plastic or aluminum trim on the top of the glovebox, if this is screwed in too tightly it makes a horrible sqeaking noise every time it is disturbed, if this sqeaking noise is what you hear then loosen the screws inside the glovebox that hold it in place and the noise goes away, if the whole glovebox rattles then you can recess the latch that the glovebox connects to by pushing it inwards with a little force, also adding electrical tape to the latch will stop any motion of the glovebox.
Seats: don't know why this helped but I put in a decent amount of plain grease into the guide rails of the seats, then moved the seats forwards and rearwards while applying the grease more, the sound died down significantly but is still there sometimes.
Armrest: this is by far the simplest one, go to home depot, buy some weatherproofing strips (the foam padded kind with a sticky side), and place them in small strips next to the holes that the armrest latches into when closed. Sound goes away completely.
Dash: I had a buzzing dash that would sometimes show up after hitting a bump, turned out to be the engine heat shield below the turbocharger, tightening the bolts that hold this heat shield in solved this dash rattling problem (which really does sound like it's coming from the dash).
Door Panels: you can do the same basic idea as I did with the armrest on this one if you find that certain parts of the door panel are rubbing against the door and making noise, place a few strips of weatherstripping and the noise is gone. The torx screws holding my door panel in place were also loose, allowing it to flex slightly, I tightened these down and most of the flex was gone, but had to place 2-3 strips of weatherstripping under the door panel to stop a "clicking" noise that they would make over bumps.
I hope all of this applies to you R guys, the only rattle I can not solve is the rear deck rattle...