Vault 92 is the features location in the quest Agatha's Song. It is a vault used to centralize musicians to keep a permanent storage of artwork.
At the front of the vault is a laser pistol, and a few medical supplies.
Old Olney is patrolled by Deathclaws. While Old Olney does not itself contain notable loot, there are a few containers and dead mercenaries that have a few weapons (such as a combat shotgun and a laser rifle).
There is also a loose grate on the ground. Stepping into it will require you to use fast travel or to walk through the sewers.
The sewers contains a Duck and Cover skill book, Prototype Medic Power Armor and a Nuka Cola Quantum.
The Republic of Dave
The Republic of Dave is a critical location to You Gotta Shoot 'Em in the Head.... It is a small fenced family who have setup a form of monarchy.
To enter, you will need to head to the front entrance and speak with the child at the front gate. A side entrance is also available on the southern or right-hand side of the fences area. To remain in the area without angering the residents, you need to speak with Dave and either pass a speech check or offer either 250 caps or a hunting rifle.
You can visit the museum for a description on the history of the republic. There are also plenty of items in the museum, including two pre-war books and a Perception Bobblehead.
An election is also about to occur in the republic. When you ask Dave for more information, he wants the civilians within the envrioment to cast votes in the election. In most cases, Dave will be elected; to change the outcome, you will need to suggest to one other person to run for presidency – then remove all votes for Dave when the ballots are being counted. You will receive a unique hunting rifle, Ol' Painless if you change the election outcome.
Chaste Acres Dairy Farm
This location is a home to a few raiders.
You can find lawnmower components required for the Shishkebab, and Grognack the Barbarian book within the barn.
A copy of Pugilism Illustrated is in the silo.
MDPL-16 Power Station
This is a small power station. The substation within the area has Nuka-Cola Quantum and a workbench, and an unlockable safe with various supplies. The high-tension power lines to the north and south were long destroyed.
Greener Pastures Disposal Site
This location is radioactive. While it has both fencing and signs before you enter the radioactive area, some leakage has caused the grounds to the northeast to become hazardous as well.
In one of the first trucks on the south, you can find a radiation suit and a big book of science.
On the western edge of the disposal site is an office. You can enter to get a Nuka-Cola Quantum, scrap metal, and an agility bobblehead. There is also a workbench and an unlocked safe.
This is a small diner protected by frag mines and inhavited by raiders. Once you clear out the raiders, you can rest here safely.
Don't forget the Keller Family transcript, located on a desk at the back.
Relay Tower KX-B8-11
This tower is a radio station. Unlike the other signals, this radio tower broadcasts a voice message rather than a Morse code signal. The drainage chamber mentioned in the signal is to the south-east of the tower.
Look for a Medical skill book and a pre-war book. There are also some medical supplies and ammunition.
Minefield is a small village that is filled with fragmentation mines within and around the village. It has one inhabitant, Arkansas, who snipes intruders from a central vantage point.
There are a few houses that contain usable loot in locked saves, including pre-war books.
Temple of the Union
This location is features in the Head of State quest. Unlike other locations, you can't use Fast travel to leave the area.
To enter, mention to the guard that you want to enter for a place to rest or trade. For the key to the front gate, speak with Hannibal (on the second floor) and say that you will protect the Temple of the Union. If you don't, you won't be able to leave peacefully aside from jumping out a second story window.
When you complete the associated quest, the temple will be abandoned and the residents will move to the Lincoln Memorial. Also, you can tell the slavers in the memorial that the escaped slaves are holed up in the temple.
Alien Crash Site
An alien ship crashed somewhere to the west of Greener Pastures Disposal site and north of MDPL-13 Power Station. It contains an Alien Blaster, the most powerful weapon in the game, along with power cells for the blaster.
The weapon is extremely powerful, but ammunition is in limited supply. You can get extra ammo from Fort Independance after aiding the outcasts.
If you purchased the Mothership Zeta addon, you will be transported onto the alien mothership.