Now why does iPhone comes with the notepad and not the Touch?
This was a disappointment with my new iPod Touch, but I've found a way to use the Address book as a alternative until Apple may add this as an upgrade.
Create a new group "Notes" in the Address book. Add a new contact with a name only and text in the note box. Sync the contacts with "Notes" as one of the selected groups.
or just jailbrake it like vigilante said.