The nectarine's just a fuzzless peach. Wikipedia says so:
http://en.wikipedia.org/wiki/Peach. (And the Talk page is all about nectarines, with no specific contradiction that it's a subspecies of peach.)
A pluot is a hybrid of a two-thirds plum and one-third apricot.
An aprium is similar, but it's two-thirds apricot and one-third plum.
Miranda (who started typing "Nektarine" before she stopped herself)