Here is how the long haul aircrafts 74A, 77A, and 34B will be deployed for long haul routes (flight duration of 10hrs or greater on nonstop) May 1st through Oct 30th, 2010 as of today:

74A
CX251/250: LHR Daily
CX253/254: LHR Daily
CX255/252: LHR Daily
CX261/260: CDG Daily
CX271/270: AMS Daily
CX289/288: FRA Daily
CX838/839: YVR 3x weekly
CX870/879: SFO Daily
CX872/873: SFO Daily

77A
CX235/234: MXP 4x weekly
CX749/748: JNB 3x weekly
CX820/827: YYZ 3x weekly
CX826/829: YYZ Daily
CX830/831: JFK Daily
CX840/841: JFK Daily
CX880/881: LAX Daily
CX882/883: LAX Daily
CX884/885: LAX 3x weekly
CX888/889: YVR/JFK Daily

34B
CX107/108: AKL Daily
CX117/118: AKL 3x weekly
CX257/256: LHR Daily
CX263/262: CDG 3x weekly
CX293/292: FCO Daily
CX749/748: JNB 4x weekly
CX838/839: YVR 4x weekly

There are rumors on the Hong Kong Aviation Board that LHR may get the 77A for CX257/256, but till now that rumor still hasn't become a reality. So as of now those flights are still 34B. I apologize if I might have missed some flights that belong on the list and feel free to add. Hope this helps fill in some needed information for the destination section of the FAQ.