The new iPhone OS version 3.0 software arrives on 17 June. Get it and your iPhone will have over 100 new features.
Like:

• Cut. Copy. Paste
  text, numbers and email addresses between applications
• Search
  Find contacts, apps, phone numbers, email addresses and more. Anywhere on your iPhone.
• Landscape
  Read and write texts, emails and picture messaging holding your iPhone sideways.
• Longer battery life

And for existing iPhone 3G customers, available from 19 June:

• Picture Messaging (MMS)
  Send photos, contacts, sound files and location with MMS messages.
• Internet tethering
  Get your PC or Mac online using your iPhone 3G as a modem, (This is not free by the way).

source: o2.co.uk

Also read the facts and rumours posted earlier.