What Are Your Favorite Fun, Cool Weather Activities to Do with Kids Indoors?

Lots of Crafts and Play Doh, painting , etc..(especially Thanksgiving/Christmas stuff)
Board games
Cooking
Reading
We make every year a little home made book with "20 things we have accomplished this year"; everyone writes it down. We use different kind of crafts to make it, it is not always a book, sometimes a tree or a golden sheet, etc...Everyone uses his/her imagination. This takes time....but it is fun since you think"how many????" Twenty is a lot...?but if you count simple things you get to that number (i.e. my 6 year-old boy learned to read last year and he proudly wrote it down, not perfectly but he did it on his own; I was more patient with the kids..that is an accomplishment!, etc...).
Building legs, blocks, etc...
That is what we usually do, but weather permitting, we go outside as much as possible.

We didn't do a lot of indoor stuff at home. I liked to go bowling, indoor mini golf, swimming, playstructure, rock climbing, the library, and museums when the weather was bad. I always looked for coupons and memberships so we could do these activities without spending a lot of money.

Okay, mine is not the most creative idea, but my kids love to go to Ikea! If you are itching to get out of the house, you can take the Max to Ikea and let the kiddo walk the whole store. I love it because I get great home organization ideas. My kids love to play at the play stations and toy area.

I don't know if it is nationwide, but out here, kids eat free at Ikea on Tuesdays. I refuse to go to Ikea on the weekends, but on the weekdays, we pretty much have the whole to ourselves.

Like Sherri G, I liked, no NEEDED to get out of the house a lot, so we did a lot of the stuff that she mentioned. I know Portland winters are foggy, cool and wet, but I think it's still a good idea to get outside some, you just need to dress for the weather.
Other than that we did a lot of cooking and baking, and my kids loved to build indoor forts out of large cardboard boxes, blankets and random pieces of furniture. There was also lots of block and lego building, and paints, play doh, etc. My kids were pretty creative and independent so they could do a lot without much help from me, which freed up my time to work on my own projects (painting, decorating, reading, crafting/scrapbooking, etc.)

One of our favorites is hide and seek! We can play for hours!! Only if the dog is outside though, b/c she cheats!
We build a lot of forts.
Have Wii competitions on Wii Sports.
Camp out in the living room ~ yes, we get the tent out and have picnics inside.
We also like to bake stuff and cook some.

H., I like your style! I've always believed that being proactive makes a mom's job a whole lot easier. I love your seek and find idea....my son would love that!

It doesn't get cold as often or as long as other parts of the country than here, but I do have my own list of go-to's:

1) I bought a book of easy science experiments, from mixing liquids and materials to magnets and paper things. I put materials and instructsion ina baggie, noted any missing ingredients (some experiments call for things I normally don't have on hand or wouldn't be wise to keep a large stock of just sitting around) and have them at the ready.
2) I have a bucket of all kinds of cheap paper goods - plates, straws, cups, and some rolls of tape and we like to build things with them on a rainy day...its like of like legos or lincoln logs.
3) I do have a list of indoor places around town (for hot and cold weather) with their telephone number and fees written next to it if we decided to get out of the house at the last minute.
4) BALLOONS! I always keep a pack of balloons on hand...they are so good for playing games or just volleying them back and forth to each other. We play golf with balloons, baseball, volleyball, tennis. I like tie a string around them, hang them from the ceiling of different heights, and have my son run around the room with his nerf gun and try to shoot them as targets.

Yes, I saw this on Pinterest - It is called 'spy training' and it is all these indoor activities that let your kids pretend to by spys in training. I can't wait to set this up for my boys!! FUN:)

Homemade playdough is always popluar at my house. We use cookie cutters, little play dishes, mini rolling pins, etc. My daughter helps make the play dough as well.

We also like to decorate the kitchen windows with window clings. I saw on pinterest that you can make your own window clings so we may try that this year.

We also like to have tasting "parties". We'll do something easy like pop some popcorn and divide it into three bowls. One bowl might be taco flavored, one bowl might be cinnamon sugar, and the last bowl will be parmessan cheese or something along those lines. Then we vote on our favorite. There are so many easy popcorn "recipes" online.