what programs can i use to bind the newest SMF version and joomla 1.5.6? You know so people wont have to make 2 logins?
none...
There are no officially-supported tools here for a Joomla!/SMF combination due to some licensing difficulties from the Joomla! developers. There are several outside tools, but I am not aware of their status.
I don't believe any of the unofficial bridges currently support single-signon or single registration
I believe at least one of them does, but it is in the same precarious licensing situation.
The best recommendation at this point is to wait for SMF 2.0 and research whether or not Joomla supports OpenID.