I've replied to Travel Bloggers Unite's tweet but I thought I'd offer a few more suggestions. The climb up the stairs to the dome of the Sacre Coeur is most definitely worth it for the views. You really do get a bird's eye view of the city. The Musee d'Orsay is also a great place to spend some time. At least half a day depending on how much you like art.
If you're planning to use public transport pick up a Paris Visite ticket for savings.
Paris is fantastic. I hope you have a great time. For some tips on Paris on a budget check out my blog www.thehumbletourist.co.uk