The Three Gorges Museum is excellent, and free.
Luohan Temple is nice but renovations have been a little heavy-handed.
Perhaps the best thing about Chongqing is the food, especially if you do like spicy. Lots of food streets. Find one and try a variety of the snacks, or a hotpot.
Wulong, a town to the south east, has many outdoor adventure options and make a great getaway from the city.