This would be my favorite Las Vegas attraction.
I could stand and watch the fountains for an hour plus sometimes... The Bellagio website lists times and songs, they are played randomly but the night shows are every 15 minutes apart so there is time to catch a few in a row. The day time shows are great too, especially when the sun is out and a rainbow can be seen while they're going.
My two favorites are "Time to say goodbye" and "Viva Las Vegas"
Other places to catch this attraction with different views are from the Eiffel tower across the street...you can hear and see the show from up there, as well as outside at Paris' Mon Abi Gabi restaurant. I was able to catch the fountains while on the High Roller this past week and that was super cool as well. Do NOT miss out on this while in Vegas!