The picture is not too clear but I'll have a go at it. I think it might be a Euphorbia mammillarias, varigated.

Dawn

I think Dawn has it right.

Afterthought: Dawn has it right except for spelling. It is E. mammillaris

Here is a link that might be useful: E. mammillaris

Dear Brad,

Dawn had it operatically correct - E. mammillarias cv. 'Toscanini'

My first impression is Euphorbia baioensis, though it is difficult to tell from the small photo as the stem details are not clear.
The branching/clumping structure looks more like baioensis than mammillaris to me...
How about a larger or closer photo?
Peyton