Quick question: I have adsense running on a forum I run which I have a partner who owns a percentage of it. So we will be splitting the revenue from the forum. However I also have other sites that I am sole owner of that are running as well. Is there anyway you guys know of to figure out exactly how much the forum is making so that we can split it?

You can create "Channels" in adsense.

Create a channel for your forum, and you will be able to see your "forum-only" stats in a few days.

Read the https://www.google.com/adsense/faq the last section talks about channels.

any Canadian's here that make a fair bit of adsense know what happens as far as tax issues go? I am not sure if I have to claim this or run this through the business or not.

While I am not 100% of exactly what the canadian rules are, we just include whatever we get from our sites that use adsense as advertising revenue, along with the banners, etc on the sites.