Mt. Whitney, The Sierra Nevada & Beyond...” Message Board is a useful source of information.
The following threads discuss the Cactus to Clouds hike:
http://www.mt-whitney.info/viewtopic.php?t=1117
http://www.mt-whitney.info/viewtopic.php?t=975
http://www.mt-whitney.info/viewtopic.php?t=962
http://www.mt-whitney.info/viewtopic.php?t=941
http://www.mt-whitney.info/viewtopic.php?t=932
http://www.mt-whitney.info/viewtopic.php?t=838
http://www.mt-whitney.info/viewtopic.php?t=223