They've been to Versailles. They walked Montmartre and visited Sacre Couer. They've been to St. Chappelle and Notre Dame de Paris. From the blog of The Lovely Daughter, who is in Paris en route to Prague:
On Thursday we were originally going to go to a bunch of museums, but we met two guys from our hostel who were going to Versailles and and decided to go with them. We did not decide this until after we had gotten on the metro, so we hoped off the metro randomly and waited for them. It was a fantastic spontaneous decision and we had a lot of fun.
Last night was pretty fun at the hostel; we met several guys from all over the U.S. (South Carolina, Texas, Pennsylvania). With Kelsey, me, and Dylan who we met the other day (he's from Minnesota) we had a good portion of the U.S. represented. Its funny how you meet people from your own country whom you would never encounter at home when you are abroad. We had a really nice night in...after our long day of walking.
I am experiencing SUCH an intense sense of lost and wasted youth!