Hello. My name is, Mike. I'd like to try and assist you by providing some additional information. Essentially what you need is an open source forum solution. As for what is best, ***** ***** really subjective. Only you are going to know which solution best fits your needs. There are so many options out there. You really need to determine what your core requirements are and go from there.
Here is some information to help get you started: http://hellboundbloggers.com/2010/05/free-open-source-forums-6892/
Another thing you need to consider is that with most of these open source ready out of the box solutions, is that customization is fairly limited unless you are proficient in coding. So you want to find a solution that is versatile enough that allows you to customize it in a way that it integrates well with your current website and online identity (colors, fonts, logos, etc.).