Many businesses use Microsoft SharePoint to enable collaboration over Office files. Dean Beeler's $15 SharePlus Office Mobile Client lets iPhones be part of that collaboration. You can test it out with the free SharePlus Lite version.
Also consider getting the free Moshare if all you need to do is view SharePoint-provisioned documents, and cut and paste their text into your other iPhone applications.
ERP and CRM access
The free SAP BusinessOne app lets you view reports and content, process approval requests, and manage client and partner data in your SAP ERP system.
The free Oracle Business Approvals for Managers provides approval capabilities for expenses, purchases, job vacancies, and other tasks, as well as access to various Oracle BI reports.
TE's $1 SAPplApp provides access to your SAP ERP system after you connect into your corporate VPN, so you can monitor your business transaction data.
The free Oracle Mobile Sales Assistant app lets salespeople query customer records and transaction data, as well as manage leads in Oracle's CRM system.
Resco's $50 Mobile CRM Enterprise gives iPhone users direct access to a Microsoft Dynamics CRM server, so they can manage and monitor customer relationship and sales transactions on the go.
Mobile Edge for Microsoft Dynamics, Mobile Edge for NetSuite, Mobile Edge for Oracle Siebel CRM, and Mobile Edge Express for SugarCRM are all client apps that let you connect into popular CRM and ERP systems. The iPhone apps are free, but service pricing varies based on number of server licenses.
The free SAP BusinessObjects Explorer lets you connect into SAP's business intelligence tool to explore sales trends and the like, then share the results with colleagues.
You can access Oracle BI reports with the free Oracle Business Indicators app.
With the free MicroStrategy Mobile, you can access performance and other metric dashboards set up in a MicroStrategy business intelligence server.
Analyze your Excel, Google Docs, or Salesforce.com data visually with Mellmo's free Roambi Visualizer. Licenses start at $99 per user per year.
If you run a website and monitor its traffic with Google Analytics, Inblosam's $7 Analytics lets you track that traffic and run reports from your iPhone. The $7 Analytics Pro from Thomas Blackburn is similar, with a bevy of visual reports available.