I still can't understand why Apple goes to such great length to hide some of the iPhone's features in western iPhone. I'm referring to the popular smiley/emoticon/emoji images that are available in Japan, but not elsewhere.
But now you can easily enable these secret emoji in your own iPhone... for free!
Update: with iOS5, you can now enable the emoji keyboard under international keyboards without the need for this kind of workarounds, and here's a list of all the Emoji on the iPhone.
To enable emoji in iPhone OS 3.0 you only need to get the Spell Number App (it's free) from the App Store, and once you've executed it, enter the number:
Now, you can go to Settings>General>Keyboards
And, in the Japanese keyboard section you'll be able to enable the emoji keyboard.
You can even unistall the Spell Number App, as the emoji keyboard will remain active.
Keep in mind the keyboard will only show up where allowed (as in the SMS section, notepad, etc.)
Also, keep in mind you can use these Emoji and Glyphs to name your iPhone Folders in iOS4!