kyak or priceline
No but here's a tip, when visiting airline websites use Google's incognito mode, if a website notices you come back after already visiting, they raise the prices.
Maybe that site's design doesn't make use of cookies to price-gouge
Try going to a travel agent, or a price comparison website, they can usually find you the cheapest stuff
http://www.spirit.comCheapest flights EVER.
Even if I did they'd all be for UK airlines, so I'm afraid not