Yes there is an app for SharePoint. I guess Apple and MS made up some point and we consumer did not even noticed. Apple renders MS product beautifully. This is great for consumers. This app works both on iPhone and iPad. It makes documents easy to read. User can open all MS office documents like word, XL etc. and Acrobat too. You can quickly move between multiple sites. What has really surprised me about the app is that it works great on iPhones and it is free. Search for iShare under Business category on iTunes and you will be able to find the free app. It rated pretty well.
If you like to read more on Sharepoint apps then visit these two sites:
App site on Apple: http://itunes.apple.com/us/app/ishare/id305862898?mt=8#
SharePoint magazine: http://sharepointmagazine.net/news/microsoft-sharepoint-on-the-iphone
Apps look and feel on iPhone, see picture below: