Zuji, a Singapore-based subsidiary of Travelocity, used to allow an international flexible-dates feature that mirrored Travelocity's U.S. domestic ones (e.g. allowed year-long searches and basically listed all published fares, regardless of availability). However, last time I tried this a few months ago, I couldn't get it to work.

The reason Zuji was able to do it and Travelocity wasn't is because of US [DOT?] rules specifying that fuel surcharges must be included in a quoted fare. Because international fuel surcharges vary by date, they can't legally be included in the fare list shown by Travelocity. That restriction doesn't exist in Singapore. I'm not sure why Zuji won't do it anymore, though.

I hope something develops that allows something similar to Travelocity/Zuji's flexible dates feature, though. The 30-day-at-a-time search offered by some travel agencies and ITA is too restrictive. It doesn't matter to me whether the ticket is available in March or October, and having to search 12 separate times to see if a cheap fare is available is too much work.

Farecompare's list of fares seems like an acceptable substitute for now, but finding actual availability isn't as easy there as on Travelocity...