Flight search, owned by Google, searches a month's worth of dates, not quite sure I see the point, but trusted folks rave about it.
Some crazy cheap flights if you get the rights date / destination combo.
Cheap flight search, in French only, but seems to cover some airlines that SkyScanner didn't. Nathaniel found ultra cheap flight from Marrakesh to Marseille for example.
Jetstar are a budget airline that fly all over Australia / New Zealand and to Singapore and Bangkok (possibly further afield).
JetBlue are a budget airline that operate across most of the US.