great profile on Schlumbergeras.
I'm pretty sure this is an Easter cactus; the timing is right, and the shape of the flowers matches what I have read. These have radial symmetry, as opposed to Christmas cacti, which show bilateral symmetry.
Anyway, the flowers are gorgeous. You can see the similarity with "traditional" cacti; I posted a picture of Mammillaria a few days ago, and the flowers look almost the same, except for the size.