Tiffany: Exotic Angel used to sell Epiphyllum oxypetalum and although many times their plants are mislabeled it could be they got it right with that one.
If it's Rhipsalis, it might be Pseudorhipsalis ramulosa whose foliage turns a pretty red when grown in sun. Check out these photo's:
http://www.google.com/search?q...
More photo's here (click to enlarge):
http://cactiguide.com/cactus/?...