How to make available 1-2 specific plugins to all users

Hi:

The newby again! Running WPMU 2.8.4a with Supporter installed.

I would like to make available 1 or 2 specific plugins to all users no matter if they are Supporters or not (eg. a contact form plugin).

For example, non-Supporters are entitled to plugin 1 and 2 by default. And Supporters are entitled to plugins 1 thru 10.

How can I do that?

Thanks.