Seattle based Farecast is turning into quite a good way to find cheap airline tickets.

The core service predicts if airline prices will increase or decrease in the near future from the current prices. They added a price guarantee in late 2006 that allows users to pay a $10 fee and lock in the current low price. They can then make a purchase decision later.

This morning, Farecast is launching a new deals feature. Unlike other travel sites, where deals are generally excess inventory being dumped at a low price, Farecast is saying they’ll find particularly good deals based on their analysis of the airline pricing stream which goes through their engine every day. On their home page right now they are showing a $333 ticket from Seattle to Honolulu.

The company has raised just over $20 million in capital.