When Registering Let Users Pick Passwords

I understand that having users pick their passwords could be a security risk but I think in certain situations it is acceptable. All the code I see on this issue says I need to edit core files (the latest I can find is version 2.2) but I feel that is not a long run option since I would never be able to update my wordpress. Is there some kind of hook or plugin that will edit the registration code to allow users to create their own password?