I am setting up an event website and would like to associate two different K2 items categories with one another. My site has two item categories, events and performers. I would like to be able to list and link the performers for a particular event to their associated item page. On the performers item page I would like it to be able to list all of the event items that they are associated with.

Hi. K2 items can only belong to one category. You can try to use tags and see if they cover your needs. If not you have to look for a third party extension doing what you need.