Add some extra fields to the customer information (where their phone # and address are listed) for things like ISP, Email host, domain host, phone provider, etc. Having a field for the provider/host and the corresponding contact information would be nice.

Also have a full notes section for each customer would be nice for storing client information. Basically just put a single page of the knowledge base on each customer portal where it's a full page editable field that you can store random client information.