The answer would be one of Mambo, WordPress, Xoops (currently in beta), e107. It also appears that there is an integration (or almost complete one) with Typo3. Note that there is no more integration between SMF and the newest version of Joomla (you can run them separately though)
Thanks claudek, what do you think is easier. Since I am really not an expert and I just newbie and working as a physical therapist. I am planning to create a Physical therapy forum I have already one installed at http://cloverprime.com/healthcare/cms/forum/index.php Thanks for your help
In all honesty I cannot give you a definite answer. I use SMF with Tiny Portal only right now and it serves my needs. I would consider asking at the SMF forum itself in this section - http://www.simplemachines.org/community/index.php?board=116.0 You would get a much more definitive answer there.