Walk down Parley Street and read the experiences of the Saints who had to leave their beloved city and Temple.
Go to see a performance in the Cultural Hall which is put on by the Missionaries who serve in Nauvoo. In was fun and also very uplifting Judith P.
Go to the Temple it's really pretty! Also visit the Visitor Center!! And also go see the Joseph Smith Home, that the RLDS own, and walk the trail that leads to the Mississippi River. While in town, take a wagon ride or go Antiquing. - Jody
Some of the RLDS sites shouldn't be missed. My favorite things to see were the graves of Joseph, Emma And Hyrum owned by the RLDS church.
There are lots of fun things to do in Nauvoo:
Don't miss the opportunity to visit Nauvoo and all the sites. It is a must. I went with friends who were going to be sealed in the Idaho Falls temple. We had very special moments witnessing and learning of the saints who had leave Nauvoo. (Try and go with friends) - Jean Francois from South Africa
Be careful of all of the anti-Mormon stuff floating around. It definitely seems more abundant in Nauvoo than any where else. Plus, Nauvoo shuts down pretty early for food, etc. so keep that in mind when going. (Contributed by Emily Raymond)
You can spend a good week in Nauvoo, especially if you plan to do a temple session - Rachelle Anderson
Lots of info about the different historic sites in Nauvoo http://www.lds.org/placestovisit/region/0,10749,1778-1-1,00.html
Book any plays or other productions you might want to go see. They are totally worth it. (The Nauvoo Pageant doesn't need tickets ahead of time.) - Amber
Take your time and see everything! - Samantha Buntin