Like live feeds from satellites and whatnot
Not live feeds, but usually have topical satellite images:
There aren’t any real live feeds, like “webcam” type things, but there are many that update every few minutes and are often called “real-time”. Most of them are weather sats. Could you be more specific what you’re looking for?
Try these. Some of them are the same, but the images may come in different formats or with different information added or whatever:
http://www.star.nesdis.noaa.gov/smcd/opdb/aviation/imgs.html
Topozone.com and terraserver.com sell satellite imagery by credit card and download. Typically they offer a variety of image times (that is, some images that are decades old and some from this year and various times between), and they offer grayscale and color and false color infrared, and they offer a range of image scale and effective pixel size.
Those are some nice ones. The weather ones I guess are the most interesting.
but international, not just North America 
I’m surprised no one has mentioned Google Earth: http://earth.google.com/
Try this for international weather sats: International Weather Satellite Images
Here’s a couple for various non-weather satellites all over the world but I only recommend them if you are serious about finding satellite data and not just wanting to casually look at some images. Might be fun to browse the contents though.
http://glcf.umiacs.umd.edu/data/ (registration required)
http://earthnow.usgs.gov/ (requires java)