What would be a good movie to show at a party for 6 year olds?

go for an older Disney movie they probably haven't seen possibly

maybe something like Alice and Wonderland?

and it's not Disney, but maybe The Wizard of Oz?

There are a bunch of Scooby Doo that have been released lately you can get the classic cartoon or the movie and tie in a mystery theme to the party with guessing games, a scavenger hunt (give them a list and have them search for things in the movie-most right gets a prize) - have "ghost and hero foods" like Marshmallow ghosts and hero sandwiches don't forget the "Scooby Snacks" triskets with string cheese would be cool. Another option would be to go with Inspector Gadget and have a "spy theme" serve spy foods like kid versions of adult finger and party foods - instead of hot dogs do mini wraps, tea sandwiches can be cucumber and cream cheese, pb&J, meatballs with spaggetti dipping sauce,etc. and be sure to serve "champagne" aka Sparking Cider since spies live a glamourous life;). If the food and games tie into the movie the kids will enjoy the movie and have lots to remember after the party. Good Luck!

Holiday movies? The Polar Express, How the Grinch Stole Christmas, Home Alone, ect.

Harry Potter, Hannah Montana 3D

Basically what Saphire said. If it's G rated, it is appropriate for kids. And you said that they were six, so maybe some of the new Disney movies that have just come out, such as "Finding Nemo", "Ratatouillie", and Wall-e" (fabulous movie, one of my alltime favs) and any other Disney movies that you can find. THere is a list of numerous Disney movies on this website below... Have fun!

The goonies.

Popeye.

Crocodile Dundee.

The Three Stooges.

A Christmas Story.

Ghostbuster.

Dumb And Dumber.

Space Camp.

Abbot and Costello in Hold That Ghost . Starts slow but is a movie that's funny , scary enough for that age group and is one they'll want to watch again.

Alive

Mary Poppins.

Bolt, or Bedtime Stories, both made by Disney.

You could go with the cat in the hat, any of the princess or barbie movies, or enchanted.