NamePros.com
As their website states – “NamePros is a free online community for domain name buyers, webmasters and website developers.”
This is a good community to buy, sell and discuss anything to do with domain names. Whether a seasoned domain investor or new to the industry you will definitely want to be involved with NamePros.com
DNForum.com
Here is a snippet from the front page of their site – “If you are new to domains and looking to buy, sell and learn about domains then you have come to the right place.” This is definitely another community that you will want to participate with as you will have access to thousands of domainers and industry professionals. Make sure you have an account with DNF.com.
Digital Point
While not specifically a domain name forum this site is my favorite general purpose site that covers discussions on everything Internet related from social networks, pay per click, the major search engines (Google, Yahoo, Bing) to affiliate programs, eCommerce and of course domain names. Have a look at Digital Point.