The iPhone Fax Machine
One thing I forgot to mention just after I got the phone was that T-Mobile provides a Fax service for its mobiles. To get to the Fax function, just go to Settings>Phone>Sim Applications>Mail & Fax.
You then get into a different coloured interface than normal (all Black), you select Send Fax, and then you can then type in anything (it brings up the keyboard) and Fax it to a number. No way to attach anything though, so no good to send documents or pictures. It seems to also offer to receive Faxes as well (via your standard Mobile number), but I have to test this out more. Of course, this is not a special app on the iPhone just for Germany, this is included on all T-Mobile SIM cards, and so the service may not exist on other carriers. Still, it may come in handy one day if I find someone who really needs a fax instead of an email..