So, imagine I have a wiki library. That library has had columns added to contain other interesting information, e.g. lookups to related items in the same list or lookups to parent lists. How would I be able to include just that data on the wiki page itself, i.e. show all related items for the currently viewed page? I'm thinking about OOTB solutions (Foundation where possible), I understand I could code a custom part but I'm trying to KISS.
You could do a number of things without custom code. You could make site columns that populate field controls on a page with a filter web part sending a peice of data that populates the controls.
Or you could use a web part page with CQWP's to display the data you want from your central library. An even more elegenat approach is to place these CQWP's ina page layout along with a single filter web part that is only viewable in edit mode which feeds all the other web parts.