A340/330-300/600 - Mobile Crew Rest (MCR) container in Hold 3. In the -600 it takes up so much space you can only fit 4 AKEs or 1 PMC in the aft hold (Hold 4) which must be a larger MCR or something else in front of the MCR (fuel tanks?) as on VS
's -600s there is an MCR and space for 12 AKEs. Access via a closet door near the L3 door (emergency exit on the -300s).
A380 - fixed crew rest in Hold 3 on the right side. Access via what looks like a lav door on the right side of the aircraft around R3
B747-400 - above R5
via a corner lav door. This is pretty common on all 744s if they have a crew rest.
All Airbus long-haulers have the flight deck crew rest between the flight deck and forward galley, and you have to access it by leaving the flight deck. The 744 has the flight crew rest on the left side aft of the flight deck, and is accessed from the flight deck, without leaving the flight deck. All have 2 bunks.
On another note, the 777-200 crew rest is similar to the 744, and the 777-300 also has a flight deck crew rest above the forward galley access by a lav looking door between the F cabin and the galley.
There are always slight variations to the above, but this is what you'll find most common. Now you'll just need to find where the key for the cabin crew rest is hidden