Flexible Date Travel
Flexible Dates. Here is Dad's tool for flexible travel. YOu just select the length of stay to say San Francisco and then it shows you want the cheapest dates are. Pretty neat. The current lowest fare to San Jose for instance is $144 roundtrip!
"Europe Travel":http://www.expedia.com/daily/vacations/europe/flights-cars.asp?rfrr=-33044. These are their special fares from Seattle to London. Good to check since flexible dates doesn't work there.