What I'd like to do is make sure that a list is getting crawled and search results are displayed elsewhere. But on one search results web part in particular, filter to exclude that list's contents. Offhand looking at the refinements and basics available seems to indicate nothing of the sort is doable unless the list is utilizing content types maybe (which it isn't). Thoughts?
You can exclude any path you want in the result web part by adding a exclusion to the query.
Edit the search results web part and select change query from the menu to the right. Switch to advanced mode and add this in the end of the query:
I'm not 100% on the syntax, so just add -Path: + your path (including the right protocol) down to actual listname (exclude the list view (something.aspx)) and add a wildcard (*) to the end of the URL.