Discuss ad networks with ther publishers, and get help with any problems you are experiencing with a network.
These discussion forums are full of useful relevant information about online ad networks, and are a great place to find out the latest news and opinions in the internet advertising world.
This is the relevant forum from a great site for web publishing in general. It covers all the basis with informative articles, and these forums offer lots of great information, from top online publishers and ad industry insiders.
This is one of the oldest forums on online advertising, contains some great information, and is a place where representatives from most networks visit from time to time to get feedback on their network.