Versailles to me is practically a part of Paris being only a 30-minute or so RER train ride from central Paris right to near the palace gates. And to me one of Paris' don't miss sights. It could be a half-day though trekking aroud the gardens and park is great. the Paris Museum Card covers entrance and lets you avoid regular ticket lines- check out the Museum Pass if visiting major museums and some lesser ones. Sold at participating museums - marshall your museums in the legnth of validity your chose. Let's you skip long ticket lines at Louvre too.