Yeah i think that SMF (Simple Machine Forum) is the one of the best free borads we have today! It is easy to install and a lot of mods and components and skines too...really is ver good!
You can cheek their website :
Simpla Machine Forum
The last version is smf SMF 1.1.1
I am using SMF in one forum..if you have any question let us know..
Best regards,