We happened to have an extra crib mattress that my 2 year old recently found in the basement. We've been using it as a "crash pad" and trampoline on days that are too cold to go outside. Best of all, it slides under the bed for storage.

Alternatively, we play jumping games. We'll line up soft objects or rope/string on the floor and see how many things he can jump over. Or we jump to the tune of jingle bells. It wears us both out pretty quickly. :)

I just got some play tunnels and tents that join together kinda big but you don't have to put up the whole thing. If I need a moment to myself I put these up and and the girls play hide and seek crawl through them we also have a small play slide too. I'm also working on having them pick up after themselves and we play a game we race around to pick up stuff before the timer goes off.

We have the tents and tunnels- which are fun. But I am looking for a trampoline to keep the kids from jumping on the sofas!

The Cranium Hullabaloo game is a great one for active kids. They can play it with friends, with you or even by themselves. It is also easily understood by three year olds. Highly recommend it!

Am I a total freak? Let that kid outside to blow off some steam. I live in Michigan, but we still take children outside (of all ages, even infants) in the winter. Appropriately dressed, the kids make snow angels and go sledding for about 15 minutes at a time. The only stipulation is that it can't be below 10 F (which it rarely is anyway). I probably sound snarky, but the kids are always more tired in the Winter than in the Spring when they play all day.

I like that I capitalized the seasons like they're extra special. I also realized that I was of no help....but I forgot to mention boxes! Huge fridge size boxes always last us through the winter. Lots of climbing, crawling and decorating!

I second the Hullabaloo game. We love it here, especially since we live in a condo in Chicago where (unfortunately) I can't just send my kid outside to play without a yard or supervision. We do take long adventure snow hikes around our neighborhood, but this game is a good alternative if you need something they can do without constant supervision.

And, I'm not a ridiculously cautious parent, but that trampoline above looks like a trip to the emergency room just waiting to happen.

That trampoline is great for little toddlers just learning to bounce while holding onto the bar. For bigger kids (with much bigger hops) I can see Greta's point.

I like the dance party suggestion - or better yet, a dance party with a game of freeze when the music stops.

Also, popping bubbles in the house with big claps, little claps, jumping on them, etc.

I also sometimes let my little guy build forts with pillows, couch cushions, etc. and then knock them over and jump all over them.

And I'm not sure how you feel about video games or TV and 3 yr olds (I'm not a huge fan myself) but there are a lot of Wii games and DVDs that are interactive.

We have that trampoline and love it- it is very safe as long as you enforce the "You Must Hold On To The Bar" rule. My 3 year old is super active and it's been a lifesaver.
A friend of my son has sensory issues- apparently he needs to be very physical to get through the day. His mother bought him a bounce house that fits in the living room. It comes out when he needs to bounce and bang, then stores in a closet. They also have a swing, a rope ladder and a trampoline. They have a VERY small apartment (probably 500 sq ft) and this all fits in a closet.

lsteffen, I love the jumping games idea! I think I'll try that one tomorrow. It isn't a thing, but we are big fans of running in circles/spinning and getting dizzy. There's an obligatory lie down and regain your composure period with dizziness, ya see. :)

we have a 3.5 yr old girl who needs to be moving at all times. We have a hammock swing hanging in one room, a balance board, roller skates (she skates circles around the house, wood or linoleum floors), and sometimes we bring in a board from the garage and prop it up on two smaller boards to make a balance beam, then store it back in the garage. We have a med. size place - 700 sq ft.
We do a lot of movement and jumping games too, as well as chase, hide and seek, get out costumes, turn the radio to different pandora stations and dance!
Ditto the getting outside daily - we try to do it as much as possible.

For different sensory toys, i like this site. it has all kinds of things you never knew existed, all targeted at helping kids w/ sensory integration.
http://astore.amazon.com/vestibular-store-20

My 4 year old is the exact same way. Very high energy and rambunctious. We do go outside in the snow, but even 15-20 minutes a day outside some days isn't enough to burn off all his energy! We joined a local kids gymnastics studio - he takes one teacher-led class a week for 45 minutes of balance beam, jumping into the foam pit, yoga, summer-saulting, etc, but best of all is that included in the price is an "open play" hour on Fridays where he can do whatever he wants without the structure of the class (it's still supervised by the teachers).
We also have a sit-n-spin that gets tons of use, and one of those giant bouncy balls with the handle attached that you sit on and jump it up and down ... not sure what it's proper name is, but it's a huge hit in the wintertime.

radioriot - ha! I can never figure out if/when to capitalize seasons and I'm an English teacher. I agree, take the little ones outside whenever possible. But I live in San Diego so that is easy for me to say. We encourage jumping on the couch and have a running, jumping, climbing course that runs through the family room (it includes the couch and an ottoman). With older kids you could time them or see how many times they could do the course in three minutes or something. We'll probably be seriously kicking ourselves for teaching our daughter to run and jump on the couch when she's bigger but for now it's a good rainy day game.

Four year old and two year old boys here in Montana. :) Outside is not enough.

Obstacle courses.

We have a playlist of favorite kids' songs that involve motion. Jim Gill is good for this, among others.

Fanny tag. Put a sock in all players' waistbands, as a tail, and try to get the other person's tail first. Hilarious if you play with the whole family.

Mothering Magazine had an article about doing a full pedicure or footspa with your rambunctious little ones when you (both) need to chill out a bit.

The crib mattress is probably our favorite toy. We have one of the lightweight foam ones, and and we use it as a slide on the couch, or to make forts, or to jump off the loft bed onto...

We are lucky now to have a basement; I brought our outdoor toys in.

Good luck!

When the weather is bad we allow our son to ride his 3 wheeled Radio Flyer scooter and balance bike in the house. They don't take up a lot of space and since he isn't able to go too fast on them we don't worry about him injuring himself or the furniture.

Make dens :) Backs of sofa's make good walls. Blankets can be draped over broom handles suspended between dining chairs. Use large clothes pegs to tether blankets together. Large boxes that have been opened out also make excellent walls.