Area 51 (Nevada)

A location with lots of useful loot, but essentially no quests. Bring a few packets of RadAway; it might come in handy.

On the taxiway, you'll find a computer containing a mention of a radio station in Lovelock and a bug in your Pip-Boy (even if you've already removed it as part of the story).

The crashed plane has a jammed hatch that can be opened in various ways: blowing up nearby dynamite, using a sledgehammer or crowbar (strength check), repairing it with tools/a repair kit (repair check), or using thermite. Inside is a Motion Sensor and many other useful and expensive items.

In the second location, you first need to turn on the power, otherwise the doors won't open. You'll need scrap metal and a high repair level (65% is enough to get by without crowbar). After that, the doors will start opening, but without your intervention.

Five punching bags can be found here. Each one adds 1% to your Unarmed skill (they can only be used after clearing Area 51, otherwise it won't work). 

In the building immediately next to the power plant, you'll find an officer's notes on the floor—an interesting read. In another wing, there's a safe (7 Perception and 80 Lockpicking) containing a gas cylinder. There will be two more such safes. There's also a minigun on the floor in one of the rooms (the one opposite the room with the officer's notes).

The next location will greet you with a horde of mutants. There's nothing else of particular interest, but further on in the base, there are even more mutants.

Inside the base, you can find energy cells for an alien blaster in one of the crates.

The computer has a lot of useful information, including information about Vault 8. There's also a second safe here with a gas cylinder.

If you have a low lockpicking skill, go to the room with the pile of strange biomass. Get the ghoul out of it; you can get a keycard from him to open all the doors. You can also go to the computer (82 Erudition is definitely enough) just below and open all the doors through it.

If you've leveled up your hacking, you can immediately go up and to the right to find the third safe and some useful loot. In the desk is a sheet with passwords for all the safes. You can also find a Stealth Boy and a computer with information on the purpose of gas cylinders.

In the small room is a pressure helmet, which is needed to assemble the armor. Next to it is a device into which the cylinders are inserted, launching a gas attack. To prevent the gas attack from causing harm, you can put on a gas mask or anti-radiation suit and wander the base without worry.

The room with the computer contains a control panel (in the desk) and the ability to activate the base's self-destruct. Intelligence 7 and Erudition 75 will allow you to figure out how the turrets work, even though you left living mutants on the surface. Erudition 100 will allow you to activate the countdown for the nuclear explosion.

The computer in the side corridor will allow you to activate the force fields.

The next location has a few more batteries for the alien blaster, but the enemies here are a bit tougher. There's also an emergency exit from the base.

Somewhere in the base, you can pick up a set of blueprints for power armor (near the computer with the self-destruct switch in the desk with the force field control panel), which will save you the trouble of coaxing Phil and fighting in the VV. Also somewhere around there is a centrifuge, which replaces a campfire and a lab bench (in the lab, next to the room with the gas attack unit).

Source: doc.