I run a few small websites and have Google AdSense set up to serve adverts on several domains from a single AdSense account.
Here is how to use URL channels to track page views and clicks across your domains.
For example, let's look at the domain
davidnewland.net
If you have subdomains on the main domain then set up a URL channel for each of them
photos.davidnewland.net
blog.davidnewland.net
If everything is served from the www subdomain and there are no other subdomains then simply set up a URL channel to catch all traffic on the main domain
davidnewland.net
If there are no subdomains then do not set up a channel for www.davidnewland.net as you will miss traffic that arrives without the www (e.g. someone types http://davidnewland.net into their address bar).