Customer Relationship Management: Your customer service team requires quick access to customer data. Give them a central repository where they can not only track their cases, but also link that case data to products, accounts, contacts and opportunities as part of the 360-degree view of your customer. See Zoho CRM.
Document Management and Sharing: Centralize your support documentation and empower your team to comment and collaborate on the documents in one central wiki site. You could expose a wiki to your customers for online help documentation (that's one of the ways Zoho uses their own Wiki product!): See Zoho Wiki.