I've been using Google Flights (http://google.com/flights http://google.com/flights) lately, which lets you graph prices depending on departure date and length

I've been using Google Flights (http://google.com/flights http://google.com/flights) lately, which lets you graph prices depending on departure date and length of stay. Click "flexible dates" in the date-picker. Extremely useful and fast. Seems like adioso is trying to do something similar. Really well designed, but it seems like your servers are stressed with the load right now. I'm looking forward to trying it for my next trip :)