Hi SallyCan, I admire them every weekend at my local farmer's market and have often thought about experimenting with them to make sorbet. I have also had them in cocktails, and found this recipe for a shooter. http://www.ediblecommunities.com/hawaiianislands/fall-2007/dragonfruit-shooters.htm
I also bet chilled chunks of dragon fruit would be lovely in a salad.

Eat that thing fresh! Cut it half length wise (pole to pole), scoop out the meat with a tablespoon (making sure not to tear any holes in the skin; it should come out like an avocado), trim any skin left on the meat, then dice the meat up into 1 inch chunks, add them back into the skin, and enjoy!