I have a large dataset based on several thousand surveys consisting of hundreds of questions each.
I would like to form a classification tree semi-automatically as follows. Each node of the tree can divide cases based on a single question only (which may have multiple possible responses). I would like to build the tree manually, but I would like the software to suggest at each stage which questions might best divide the data, and allow me to select the one to use. (For example I may decide that dividing cases according to sex of respondent isn't interesting, at least at the top level, so will pick another question for the root node of the tree).
Two questions * Is there any (preferably free) software out there that does this? * Is there any software that can do this without requiring a target variable? (Which most decision tree algorithms seem to require)
 I am aware 'best' is ambiguous here. Feel free to suggest different ways I might be interested in deciding on 'best', though I am likely to be guided by the ready availability of software that implements whichever method.
UPDATE I modified title and question based on initial responses.