You do not need to pit them before freezing, but I always do. You can thaw and then pit them later if you don't want to take the time now.
Use your frozen cherries as you would any fruit you can freeze: simmer with a little sugar for an ice cream, oatmeal or pancake topping, use as a filling for strudel, chop and mix with walnuts and goat cheese to stuff a pork tenderloin or chicken breast, make chutney or cherry salsa (mmmm cherry chipotle), puree-simmer-reduce with port wine and drizzle over lamb chops . . .
Having an organic cherry orchard might make me a bit overzealous on this topic!
Be the change you wish to see in the kitchen.