(using D7) I'd like a user to be able to create and save a node of a certain content type and have it so the value or setting of one of the fields called "location" will then update the same field (or another field that tells the user the "location") that's part of a view elsewhere in the site? I'll also want to plot the "locations" of things on a map using openlayers later on. I've looked at rules so far and haven't seen how to do it with rules, but I'm new to rules. And I've seen entity reference, which looks like it takes the place of D6's node reference, but I'm not sure how to use it in this way. So how can I do this?
Sounds like you could create a rule where:
Event = Node->After saving new content
Condition = Node->Content is of type (your "certain content type")
Action = Set a data value. Use the data selector to drill down to the field that your View elsewhere is displaying for location. Hit Continue. Use the data selector to drill down to the field in the recently created content that your user has entered the location data into. Save.