On top of the back-left grave in Goodsprings Cemetery (near the water tower), at the base of the grave marker. The grave is the only one in the area with rubble on top; the snow globe can be found amongst it.
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 next to it (you must first speak with Mr. House 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 look behind you 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 towards the hole.