App and developer functionality
Peer-to-peer connectivity over Bluetooth for gaming and other info-swapping.
Paid apps will have the potential to be subscription fee-based, and can include optional paid content that can be bought from right inside the app.
Developers can now build apps that call out to Google Maps, and can also finally bring Apple-blessed turn-by-turn to the phone.
Devs can also connect with hardware accessories over in their apps now, such as a blood pressure monitor -- or perhaps a keyboard? Connectivity works through the dock connector or over Bluetooth.
Long-promised push functionality will at last be included, but apps won't run in the background.
Developers can add streaming video and audio to their apps, along with in-game voice use.

General functionality
Cut, copy and paste. At last! You can shake the phone to undo and redo the action, and it works with both text and photos, allowing Mail to send multiple photos at a time.
MMS, along with forward and delete for multiple messages.
A2DP stereo Bluetooth.
Unlocked Bluetooth functionality on 2G iPod touch.
Spotlight has been added to a new home screen page to the left of existing pages, allowing for universal search on the phone.
Tethering is built into 3.0, and Apple will work with carriers on that -- who will have the last say on its implementation, most likely.
App Store will be available in 77 countries.

Apple apps
A new app called Voice Memos which lets you record notes and reminders.
A revised Stocks app, with news stories and a landscape view.
Landscape keyboard available in all major apps.
CalDAV support has been added to Calendar, along with subscriptions support in the .ics format.
Apple's major apps have all been expanded with search functionality.
Note Sync to sync your notes.
YouTube account support.
Form auto-fill.
Phishing protection.