Is there an addon or tweak that would allow me to give me a certain group of people access to certain modules. Like how you can make it so not-registered users cant see certain blocks... basically i want my clients to be able to access a part of the web site that would be excluded from regular non-customers. is there anything out there that would do this?

I think Bob's "NSN Groups" module is what you're looking for.

http://www.nukescripts.net/modules.php?name=Downloads