Would anyone know how to go about obtaining samples of Salmonella or E. coli for purely educational purposes?
Note: I just want to look at the stuff under a microscope.
To be honest, you really shouldn't be buying such things if you're not prepared to handle them properly. If you work with a proper lab, you will be inindated with vendors trying to sell you these and many others.
But to answer your question, if you are looking to purchase many such items ATCC is an excellent resource. Not only will you have to meet regulatory requirements, but you will also have to deal with a great many MTA's depending on what you are trying to get.
In response to edit: Salmonella is actually not normally a serious pathogen to a healthy adult. It is, however, still a human pathogen and should be handled under BSL2 conditions. So if you have the funds and time to setup a BSL2 lab at your house, by all means go to town. And I hope you don't live with any children, the elderly, or otherwise immunocompromised individuals.
In response to further edits: If you just want to look at things under the scope, then I suggest you get started by making your own homemade culture plates. If you can get your hands on some Lysogeny Broth (LB), agar, and petri dishes then you can make lb plates like a researcher in a real lab (minus an autoclave but you could use a pressure cooker). These are items the public could get, but might be harder to come by.
I however will assume that you want to make your own plates from common household ingredients (I used to do this a lot as kid, whatever that says about me).
Making your own culture dishes:
1) The "plates" themselves.
Note that you won't probably be able to have perfect sterile technique at your house, but you should try to do what you can.
2) Your "Media" or Broth
Now you have your own home made culture plates! The above recipe was empirically tested by my childhood, and repeated by my son's. Not all pectin from the store may be equal, this is with Ball Classic (I have no relation to the company). I'd love to know people's results in trying it, because I might need to re-think how/what I'm doing to get it to work.
Go around your house swabbing things with sterile swabs (you can get these at a drug store), and then streak them out on plate. While it will be a little different with a swab and homemade plate, the idea is similar to what is done here.
Leave your plate in a warm wet place, but not in direct sunlight. Ideal temp is going to be around 37, but you can leave them above and below that and still get things to grow. On top of our dryer is where I leave.
After a day or so you should have colonies you can streak out on a slide and look under a scope. You will find all kinds of things this way. If you want a more formal way to put things on a slide, you can check out dry and wet mounting from a Google search.
You are actually quite likely to run into E.coli if you sample enough "areas" this way. Obviously don't eat or huff the stuff that ends up growing. Maybe you can post some fun pictures of this if you try it.