To the southeast of the blue key, there is a door leading into a flight of stairs. Head down the stairs, and you will enter a room with a supercharge in a core and a T-section to the north. Activate the switch at the south, head into the T-section, and face east to find an open doorway leading to megaarmor. (sector 127) Stepping into the secret will cause the eastern corners of the previous room to lower, bearing imps, while grabbing the megaarmor will result in a teleporter opening nearby. Enter it to be teleported to the supercharge; grab it and step off the core to return.
The switch which opens secret #1 will also open the door across from it. Head west in the T-section, take the lift, and head through the passage to find a stimpack, two medikits, five armor bonuses, and partial invisibility. (sector 154) Nearby is a small doorway leading into the north of the map.