I've done this.
FaxCash is the program being sold on the 'ol www.
I actually had a telemarketing firm cold calling offices to build my send list as you need permission to fax. I'd set up the PC's faxmodem to blast these out at 2am so the offices had it sitting in the inbox when they got to work. I even had a drawing for a free friday pizza (easy to trade this with a listing on the fax). I had a few paying clients and a fax list of 1000+ "potential" viewers of the daily fax.
There are pitfalls, like any other opportunity (too many to list here) but mail me if you want details.
I had high hopes for this one and never completely burried the idea, just been doing other things lately.