I've been to Paris twice and both times I have used this website that my parents recommended to me: Apartment Rent Paris - Short Term Rental and Long Term Rental in Paris - Apartment or Studio - Montmartre

They rent (minimum 3 night stay) Paris apartments that are furnished and done up just like a hotel, but without the hassles of a hotel. In my experience, they are larger than a hotel with more amenities and in great locations with breath taking views. They are also able to help you breakdown the area that you are looking to stay in, tell you which areas to stay away from and keep you in your price range. They are awesome at helping you find paris apartment rentals. I'll never stay in a Paris hotel.

They are amazing and since they are located in Paris, they are usually the best ones to get the 411 from. They have their numbers posted on their site in the contact us section, or you can submit a form for them to email you back OR they also have live chat help during the day.