Is there a way to allow users to subscribe to certain categories in order to receive daily updates via email? I know this not a function of K2, however I was hoping someone would know of a solution.

Thanks in advance.

It seems only MultiNotify for K2 supports email subscription for users. Unfortunately MultiNotify is commertial extensition. So I would be very gratefull if somebody can offer free analog of it.

You should use AcyMailing with the K2 Element plugin:
www.acyba.com/en/support/documentation/137-acymailing-plugin-k2element.html

Create an auto-newsletter and insert the code to grab the K2 posts.