We just booked a flight to Peru on Monday. According to Google Earth's "ruler" feature, it will officially be the furthest I have ever flown, just a bit further from Vancouver to Lima that it is to London, England (as the crow flies). But if we go to Puno, Peru to see Lake Titicaca that will be the furthest I have ever been from home (prior to that, the furthest ever was Munich, Germany).
I really want to thank kayak.com for helping me find the flight that worked best for us. Kayak.com recently added a "my dates are flexible" feature. This was something I really wanted for a long time. Especially with long haul flights some flights are only on certain days of the week to certain destinations. For example you can't get from Lima to Vancouver on a Sunday or Monday with Air Canada. We ended up going with a United flight and saved about $450. I probably would have never found those flights because I never use the sites that they were being sold on (Orbitz and cheaptickets.com). I sometimes check expedia.ca but they didn't have the United flights. Anyways, Kayak.com is SO awesome, you should try them out and tell all your friends. I have no affiliation with them, I just want them to stay in business.