Stephen Fry has recently recorded a BBC podcast about the history of the mobile phone.
It's a really great series, and I encourage you to listen to it.
At one point in episode 4, Stephen sings the Nokia ringtone.
So, here it is for your edification, and delight.
Feel free to set it as your iPhone's ringtone :-)
All together now, "Derr-nerr-nerr-nerr Derr-nerr-nerr-nerr Derr-nerr-nerr-nerr Nerr!"