The seven globes in the original game can be sold to Jane for 2,000 caps apiece, which will also add them to the snow globe display stand in the Lucky 38 presidential suite.
Snow globes found in add-ons are displayed on a shelf located directly above the snow globe stand. As soon as one is picked up, 2,000 caps will automatically be given (with the exception of the Sierra Madre snow globe, which will instead give 2,000 Sierra Madre chips) and the snow globe will appear on the shelf.
In Goodsprings Cemetery. On the second grave to the west of the Courier's (open) grave, at the northern edge of the cemetery (near the water tower). The grave is the only one in the area with rubble on top; the snow globe can be found among it, in front of the marker.
In the cocktail lounge of the Lucky 38 Casino. The snow globe is on the counter behind the middle cash register with a green lamp and some bar taps next to it (Mr. House must first be spoken to in order to gain access to this area).
Located near Dean's Secret Stash in the upper levels of Salida del Sol North. From the southern-most entrance to Salida del Sol South (inside a house in Salida del Sol North), proceed down the stairway and out to the street, then turn 180 degrees for the entrance hole in the wall above. This area can be reached by going up the stairs located around the corner to the southeast and following the rooftops back toward the hole.
Snow globes are marked as quest items and cannot be removed from the Courier's inventory (unless sold to Jane).
Due to being marked quest items, snow globes have no net weight, despite being marked as having a weight of 1 lb. (Fixed in a recent patch)
If Mr. House dies, Jane will disappear, and it will no longer be possible to remove the snow globes from the inventory. However, PC users can use the console command player.placeatme 00116a50 to spawn Jane to their location to continue adding snow globes to the stand. Should Jane still be aggressive after spawning, use console command stopcombat after having talked at her to stop all combat.
After they end up on the display shelf, the snow globes cannot be interacted with in any way.
DLC snow globes will be added to the shelf automatically and do not require Mr. House to be alive.
The Toaster in The Sink will shout out that it has a "super-rare Mojave snow globe," and all the Courier has to do to get it is reach down into his bread slot. Due to the murderous nature of the Toaster, this is more of an attempt to kill the Courier via electrocution.
The Lonesome Road snow globe is the only globe that is damaged - a large hole can be seen on the dome and the Vault Boy inside has fallen over.
Behind the scenes
“It's for the Citizen Kane reference, partially because it's especially fitting for Mr. House. He has no interest in physically interacting with the world but wants absolute control over New Vegas. Snow globes are perfect static worlds in miniature that can't be directly touched but can be (literally) turned up side down any time the owner desires.”— Joshua Sawyer
Joshua Sawyer stated that he likely came up with the snow globes, because they represent a "little perfectly controlled world," in the vein of Citizen Kane.
Sometimes you can only sell snow globes to Jane one at a time, regardless of the number you've found. [verified]