I've read lots of similar post on here before becasue I too was looking for things to do with my little one. Here are some links to some of those post:
http://www.mamapedia.com/questions/4582267876475404289
http://www.mamapedia.com/questions/11167189129207218177
http://www.mamapedia.com/questions/368196501844852737
I LOVE the library. They have books, movies, childrens CD's, etc. At that age my daughters favorite thing to do was snuggle up and read books.
I agree that just getting out of the house and strolling the mall can do wonders when you're going stir-crazy. It's a great way to get some exercise without having to spend any money.
What about taking a mommy-and-me type class. Is there a Gymboree near you?
Are there any indoor playgrounds in your area? Some of them have separate areas for the little ones. That might be something that you can look into.
As for indoor activities:
* Again, snuggle up and read books.
* If your daughter likes taking baths that could be fun for her. Throw in some water toys or make your own for her to play with. You can take an old plastic container such as a cool whip tub or magarine tub and drill holes at the bottom (or have hubby do that) and she can watch the water drip through it.
* Indoor hide-and-seek. You'll have to "hide" in obvious places. It's lots of fun to hear them squeal when they "find" you =)
* Painting w/pudding, yogurt, cool whip, etc. I see this idea alot. If you don't have any objections to "playing with food" you can sit her in a highchair and let her finger paint on her tray.
* rolling a ball back and forth can be lots of fun at this age.
* Indoor ball pit. You can take a small swimming pool OR a playpen and put a bag of those ball pit balls to make an indoor ball pit.
You should check out the The Toddlers busy book by Trish Kuffner. She has lots of ideas for indoor play ideas.