There are seven snow globes in total scattered around the wasteland.
1. Goodsprings Cemetery- On one of the left graves from where you enter.
2. Freeside (Old Mormon Fort)- As soon as you enter the fort turn right and go to the end to find a door leading inside. The globe is on the second floor.
3. The Strip (Lucky 38) Behind a lamp on the cocktail lounge area of the Lucky 38.
4. The Strip (Vault 21)- The globe is in Sarah's chambers pickpocket the key off of her if you cannot pick the door.
5. Nellis Air Force Base (Museum)- When talking to Pete on the quest 'Volaire!' be sure to pick this one up before leaving.
6. Jackobstown (Lodge)- Inside immediately in front of you on a counter.
7. Hoover Dam (Visitor's Center)- Inside immediately in front of you on a counter.
Note: Turn the globe's in to the securitron in the Lucky 38 for 2,000 caps a piece (14,000 for all
Here is a video guide in case these descriptions are not enough (credit goes to OmeGigaSavior on YouTube I did not make the video).