Steve
You are caught in a chicken and egg situation, as inevitably all Web 2.0 sites are - you need users for it to be worthwhile, but it needs to be worthwhile to get users. Have you any plans afoot to get the user numbers up quickly so there is something to come back for?
I wish you well as it's a tough cycle to break. Luckily, we are up to nearly 500 members on our lead and referral website after a couple of months in test. We now have some tools for inviting contacts to join you on our site, which will be pivotal in growing the member base -- each new members brings some others. Otherwise you have to win over each member in turn. I wonder if you can incorporate the same in your site?
You can view how we have done it at
https://www.wecando.biz/my_contacts.php?page=2 (you'll need to be registered to see this unfortunately)
Regards
IH