If this is a one-time need, kinkos and some office-supply chains will fax for a fee.
If it's an ongoing need, buy a modem (external or card) and use it just for faxing.
Like Bill says, running fax servers cost money so people like eFax charge you to use them. There are (were?) some scattered free fax servers as of last year (search archived "fax free" here and Off-Topic) but they were volunteer so (a) only in some cities (b) not likely to remain avaialble as the volunteers move or decide to stop spending money to give away faxing.