I use MyBB Forums on a fansite that I run and would highly recommend it to anyone looking to install a discussion board for their own projects.

At present, I help to maintain the tutorial for VBNavBar for MyBB 1.6, which creates a vBulletin-style dropdown navigation menu.

There is also a version available for MyBB 1.4.14 but this is no longer supported.

A version for MyBB 1.8.x may be developed in the future, time allowing.