phpBB (short of php Bulletin Board) is one of the most powerful and commonly used forum systems nowadays. It is suitable for newbies as well as more technically oriented users. With it you can either create a simple form for you and your friends or more advanced forum for larger communities. phpBB is an open source project and can be used for FREE.

Forum Administration - phpBB has powerful but at the same time easy-to-work-with administration panel. With almost no efforts you can create unlimited number of forums and categories, set permissions, word sensors, mass emailing and smilies, polls, and much more. From there you can also ban access by IP, email address or username. If you would like to see how phpBB works, here you get phpBB forum pre-installed and activated in less than 15 min.

Security - as you might know the security of any forum system is a theme of a highest priority. phpBB is designed with strong authorization system and high encryption that helps to save all passwords save. It is also supports URI-based and cookie sessions.

phpBB themes - you can choose and set the outlook of your forum according to your needs. There are a lot of free and paid phpBB themes available on the Internet which you can use. Also, with phpBB you will have access to the CSS so that you can change colors and fonts yourself. The templates within phpBB are separated from the rest of the php code and new styles and themes can be easily created or integrated.

Members - phpBB has the ability to contain unlimited number of members. With phpBB each one of your community will be able to create and edit his own profile, create avatars, send private messages to other users of the forum, etc. They will not experience any difficulties posting and managing their own posts as phpBB was created very user-friendly.

PhpBB developer team has done a great job... –  PhpBB 3 Review