The guide has help for Phone, Mail, Safari, iPod, Applications, Settings, the Wi-Fi Music Store, and some Troubleshooting tips.
I even learned something new: you can scroll to the top of web pages by
double-tapping the title bar. Nice!
Update: Major poopie! Apple has taken down the site for some inexplicable reason. I'll try and find out where it's moved to (or a mirror) and get back to you.
Update 2: It's back, and its contents are updated for the new iPhone software. The new guide includes tips for enterprise users, and for using the App Store. It seems to be oddly not fitting in MobileSafari's display window very well, but hopefully that will get sorted out soon.