For an overview on using VoiceOver on the iPhone watch this Apple video.
iPhone User Guide for iOS 5.0 Software – Accessible PDF
Keyboard Shortcuts to Speed Up Typing on an iPhone or the iPad
Getting Started with the iPhone: An Introduction for Blind Users - A book by Anna Dresner and Dean Martineau. National Braille Press $18.
AppleVis - A community-powered site for vision-impaired users of Apple's iOS devices.