Show a view on a custom nodetype only if the logged in user is the author of this node
You just need to add an argument to this, passing the logged in user's uid. In Drupal 6, views 2 you used to have to reverse engineer this and add custom php into the argument handling code but this is built into Views 3. In your view: 


Add Contextual filter, 'Content: author uid'
Select 'provide default value', type 'user id from logged in user'


This will find the uid of the logged in author and pass that as an argument to your view, restricting the view results to only items that were authored by the owner of that node.