I am mainly interested in other people's suggestions but threw out a few myself. I recently was able to get Shiranui from UCR, so it hopefully will become more readily available to all. While mandarins do great in my environment, I have had a bit of a tough time getting oranges to fully develop appropriate sweetness. I have heard anecdotal evidence that Rotuma can achieve this even in relatively cool climates. This mainly came from Axel at the cloudforest site who stated Rotuma was one of his best tasting oranges even in the cool Santa Cruz mountains.
-Brett