A viewer wrote in complaining about soap suds backing up in her sink, another complained about the suds backing up in the basement floor drain.
Suds are something that drains have trouble flushing out, because they float on top of the water and tend to pile up in the pipes. First you should try to reduce your use of soap. Really. Look at the first photo above. The left and the right are photos of the same dishwasher, one with far too many suds, the other just right. There should be just a suggestion of suds on top of the water in both dishwashers and clothes washers, any more and you actually clog the machines and cause them to not clean as well. In addition, the overuse of soap can actually shorten the life of your appliance, because of the clogging and scum build-up.
Now, if you can't reduce the soap, maybe because it is coming from an uncooperative neighbour, there are things you can do to stop them from backing up. Under the sink, you can put in a back flow damper. This lets water out of the sink, but nothing back in. They are easy to find in hardware stores and plumbing stores and you can find PVC ones that match common PVC sink drains.
For the basement floor you might one to install a Dranjer. This is like a back flow damper but it can slip into the floor drain right below the grill. It is designed to stop radon gas from coming into the room, but is quite effective at stopping soap suds as well. If you have a Cappuccino maker, the most important thing to remember is the need to clean both the outside and the inside of the milk foaming nozzle. If you don't run a pipe cleaner or something up inside that tube, it will quickly plug up.
Have you ever wanted to clean off the face of a steam iron, particularly if you didn't want to admit that you used it for a glue job? Make sure to hold it face down while cleaning so that nothing goes into the steam holes. If you hold it face up, all the junk that you send into the holes will come out on the clothes with the next ironing job.