Do you like Fly4Free, but you rather focus on specific destinations? Use this Chrome Extension.
Using this extension you can pick a few interesting keywords and let Chrome warn you when something comes up matching your interests.
Starting with version 1.1 this is how the extension is going to act:
a) Get the RSS feed that the user want b) Parse the titles and look for relevant keywords c) If a relevant title is found, check its link against a local cache. If it was previously stored, ignore it. Otherwise, add it to a list of interesting deals and show a notification.