Travel Rental Network has a nice website and we paid $350 for a 2 year subscription to list our Florida vacation rental property.
The results have been dismal to say the least.
From July 2012 to December 2013 we have received 3 inquiries, all for periods that were already rented.  They only have 180 properties listed in the Disney/Orlando so only 3 inquiries from the 150,000 they claim use their site is an incredibly small number.  They also claim to be affiliated with IATA, nonsense!

Perhaps not a exactly fraudulent operation but pretty close IMO