Germany1116,
I must respectfully disagree with the reply given above by Mandyk01a.
This comment (quoted below) is referring to the Paris Pass NOT the Paris Museum Pass (easily confused except for the price!):
I agree, get the Paris Museum pass which includes metro and buses (option for the Hop on Hop Off bus). Then purchase your metro ticket to Versaille the morning you go out there.
The Paris Pass is very expensive & not recommended, especially if your intention is to travel economically.
However, the Paris Museum Pass is a good idea if you plan to visit a number of museums & monuments, and it covers the Versailles castle, (but it does not cover transportation) & it will allow you to skip most lines.
Here is the official website for the Paris Museum Pass:http://en.parismuseumpass.com
One more thing: If you're traveling with children & they're younger than 18, you do not need to buy a museum pass for them, because they can enter most museums for free (may need to show ID as proof of age).
You may still require to obtain your children's 'free tickets', at a few places.
Have a wonderful trip!
Priscilla