How to list all nodes of nodetype A which has the current node referenced?
Simplest way would be to make references two-way. To do this, use:


Corresponding Entity References for Drupal 7
Corresponding node references for Drupal 6


That way, current node will reference all nodes that reference it - and from this point creating a view is trivial - or you can simply display the field created for back reference, without need for a views module at all.

Other way is to use Views. Create a view displaying nodes from content type A, add argument content reference field > provide default argument > node ID from URL and display this block view on the nodes from content type B.