I have traveled quite a bit back and forth to Europe and the cheapest flight I found was with Air Transat, if you are not picky about comfort. I think I paid about $700. Zoom is a lot cheaper but I never could find a flight that would fit in with my schedule. KLM is a great airline but a little pricier... Air France is waaaay expensive!!
good luck!
Finally engaged: Feb. 12 '08 !!!!
Marrying: Sometime Spring '09
Big day: May 18th 2008!