Musee d'Orsay has a large collection of impressionist art and IMHO is a MUST museum to see--it is open late on Thursday nights (the night of your arrival), so you can save that until the evening (assuming jet lag hasn't conked you out). There is a company that runs "hop on off" buses that pass the important sights, so you can get a quick run by for two days. http://www.viator.com/tours/Paris/Pa...f=02&aid=g3254 is their internet address.
Another museum open late nights is the Pompidou Center if you are into avant garde art this is also interesting.
You really can't see too much of Paris in even a month let alone a weekend--so you have to make compromises: two areas to see might be (1)the Latin Quarter, (2) Montmartre.
PS: The major department stores also have Thursday as their late opening night--if shopping is your "cup tea", browsing through the ones in central Paris can also be fun.