You can send a fax via a web service. You can send faxes via providers like Sipgate for example: www.sipgate.de
I expect there are many such providers.
You can send faxes from some DSL Routers, such as the FRITZ!Box. That is much cheaper if you have a flat rate connection already, and perhaps more secure than a web service.
There are numerous how-tos on the web, such as: http://www.wehavemorefun.de/fritzbox/FAX_über_die_Fritzbox