Have you tried killerstartups.com? For about a hundred bucks you can get a few thousand pageviews. I used their service and was pretty happy. There are also other similar sites. They are not as effective but each would bring a few new subscribers.
Ours is a B2B product for Oracle PL/SQL developers. It is a niche that does not fit the demographics of killerstartups. So the conversion rate wasn't all that great but it helps to get the word out. We had about 250 visits in the first days of our web site being up which is not bad by our measures.