I am planing to give access to my registered members as contributor. They will be able submit any post for review. They can modify their profile. When I let the registered users as Contributor, they can access to one of my plug ins. How can restrict their access? or Could it be possible for me to give these users particular facilities?
Usually the access is defined within the plugin itself. You'll find in the code a check (or not) of the users role. Here's an example from the user-photo plugin function userphoto__init(){ if(get_option('userphoto_override_avatar') && !is_admin()) add_filter('get_avatar', 'userphoto_filter_get_avatar', 10, 4); } PHP: In this it looks to see what has been saved into options and checks that the user isn't the admin and adds a filter to swap out the avatar. You can use similar logic to say if the user is an admin then add_filter ... to give the plugin functionality.
I use wish list member on my blog and I can create many levels of authorization and membership. It is pretty easy to install and has so many options you can choose from to help separate members.