NOTE: This suggestion is for JIRA Service Desk Server. Using JIRA Service Desk Cloud? See the corresponding suggestion.
Currently there isn't an easy way to display multiple portals to customers. Please enhance the product to provide a 'portal of portals', as in some way to display multiple portals to the user.
Allow a Global Customer Portal Page with Links to Multiple Helpdesks
As an admin I want users to be able to easily access multiple Customer Portals
As an admin I want to have multiple projects in one Customer Portal
Basic CRM functionality