Fax from your PC

Fax using a Web Service

You can send a fax via a web service.You can send faxes via providers like Sipgate for example:www.sipgate.de

Sign up for the free basic package.
Send Faxes for a small charge (>50 cents)
Use VOIP to call other VOIP users for Free
Use VOIP to call Telephone numbers for a small charge

I expect there are many such providers.

Fax via a DSL Device

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