Best places for cheap flights?

Hey guys,

Hubby and I need to travel to the US in October for my best friend's wedding (I'm matron of honor ) but our budget is EXTREMELY tight. I'm concerned that I will end up going alone.

Does anyone know of any good sales going on right now? Or any great discounted airfare websites? I've been looking around and the cheapest I can find is about £410 each... We could do it, but it would be difficult.

Thanks!

Seems to me I read a while back that Expedia and Orbitz and similar sites will track what you look at.  If you don't choose the cheap flight when it is first displayed, if you look around for better then come back to it, it will be only display the more expensive flights.  Is that true?  Seems to me it's always better to join a Frequent Flyer Club because they will automatically email you when they have sales.  It's free to  join, so why not join several?

There isnt a place that is always cheapest, of course, but I rely on Kayak and always check Vayama seperately.  Vayama has had some really good deals lately.

Have you tried lastminute.com?  I had to fly to Michigan back in May and found a round trip ticket for £330.