We managed to get a small group of active users just by word of mouth (~30 users) and getting some friends on board (~20 users) for https://www.tripscovery.io.
We got some feedback (mostly UI things) and learned that our infrastructure, which consists of the cheapest Linode server and a mysql db, performs very well so far.
We are going to try to integrate more flight providers in the future to support more destinations. That way we can allow access to more users that are currently waiting for their city to be supported.