Excerising quietly at home... ?!?

You can get a dumbbell set
You can google "body weight exercises"
Exercise bikes are relatively quiet.
P90X or other video tape based exercises are fairly quiet
In good weather, if you can get away long enough, taking walks outside are great, even if only for 5 minutes at a time.

http://www.nerdfitness.com/blog/2011/03/10/angry-birds-workout-plan/

The loudest thing in this workout plan is jumping jacks, and if you really can't do those for fear of waking the kids, you can do something a little different to warm up. Arm swings, military march, etc. And the good thing about this particular workout is that you can do it whenever you have 2 to 5 minutes free. Do it while you watch tv, or while you're waiting for dinner to cook, or whatever.

I live in an apartment with neighbors downstairs. I got a set of rubber mats and they work great. I can jump and run on them without disturbing anyone. (They're like the ones for children sold at Toy R' Us or Amazon). I think they would muffle your noisy floors. You could also try yoga, which is pretty quiet, and get one of the thicker yoga mats. Good luck!

rubber floor mats. genius. why didnt i think of that!?

http://www.nerdfitness.com/blog/2011/03/10/angry-birds-workout-plan/

The loudest thing in this workout plan is jumping jacks, and if you really can't do those for fear of waking the kids, you can do something a little different to warm up. Arm swings, military march, etc. And the good thing about this particular workout is that you can do it whenever you have 2 to 5 minutes free. Do it while you watch tv, or while you're waiting for dinner to cook, or whatever.

I just checked out this site. Looks like he has some great advice.

I live in an upstairs apartment and no sound barrier between floors so I'm always afraid to disturb the neighbours. My husband works nights, so sleeps during the day. My floors are also very creaky and squeaky! Only thing I have found to be completely quiet is the elliptica and Pilates. Treadmills take a pounding. Bikes sounds like a loud fan is running and I don't have to tell you what an aerobics workout amounts to in terms of noise. That said, I still do it.

I try to do the aerobics when the neighbours are out so they don't hear me but ive talked to them about it and they don't mind the noise, as long as its not after 9pm. I have a bicycle on an indoor trainer with an elliptical in the same room and that whole room is padded with foam mats (the puzzle piece ones). As long a my husband is sleeping before I start it doesn't disturb him. As for the kids well...they'll live

A mini trampoline would be good for anything you do that involves jumping/jogging in place etc, or a really thick floor mat.

I'm in a similar situation and right now I'm doing the 30 Day Shred - there are jumping jacks, jump rope, etc. and I've just replaced them all with different types of boxing/light jumping in place.

Walk at Home DVDs by Leslie Sansone - these are low impact aerobics. The "routines" are so simple you can mute the sound & use an MP3 player with earbuds. Here's a short sample:

http://www.youtube.com/watch?v=PnsfbneFQ_8&feature=related

I love my puzzle mats. They do come in different thicknesses (try a sporting goods store for thicker ones). But you can find these many places, I even saw some green ones in the camping department at K-Mart.