Where is a good place to look at cells in action? (details inside)?

A 200x microscope is certainly enough to see bacteria, but you're totally right in that without staining, they are nearly impossible to see. A lot of yogurt actually doesn't have live bacteria in it - even the ones that do have only a miniscule amount (relative to the amount of other stuff that is in there), so you wouldn't be able to separate it out from the yogurt to see it. The sperm thing is pretty disgusting, but hey, whatever makes you happy... Probably your best bet as far as seeing replication and such is to look at bigger organisms like protozoa (amoeba, for example). The place we used to get these back when I was in middle school and high school was from pond water. We weren't too careful about it back then (or at least I don't remember being), but you should be kind of cautious if you are going to do so, as there can be some pretty nasty stuff in ponds that can make you very sick, so wear gloves, wash your hands afterwards, and don't use containers/surfaces where you are going to put food later.